diff --git a/spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/MeterValue.java b/spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/MeterValue.java
index 94ad8dd97578..d01b188cded7 100644
--- a/spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/MeterValue.java
+++ b/spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/MeterValue.java
@@ -86,11 +86,11 @@ private Long getTimerValue() {
 	 * @return a {@link MeterValue} instance
 	 */
 	public static MeterValue valueOf(String value) {
-		Double number = safeParseDouble(value);
-		if (number != null) {
-			return new MeterValue(number);
+		Duration duration = safeParseDuration(value);
+		if (duration != null) {
+			return new MeterValue(duration);
 		}
-		return new MeterValue(DurationStyle.detectAndParse(value));
+		return new MeterValue(Double.valueOf(value));
 	}
 
 	/**
@@ -103,11 +103,11 @@ public static MeterValue valueOf(double value) {
 		return new MeterValue(value);
 	}
 
-	private static Double safeParseDouble(String value) {
+	private static Duration safeParseDuration(String value) {
 		try {
-			return Double.valueOf(value);
+			return DurationStyle.detectAndParse(value);
 		}
-		catch (NumberFormatException ex) {
+		catch (IllegalArgumentException ex) {
 			return null;
 		}
 	}
diff --git a/spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/MetricsProperties.java b/spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/MetricsProperties.java
index c4c0b2c2f4e8..d18b4b5720fb 100644
--- a/spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/MetricsProperties.java
+++ b/spring-boot-project/spring-boot-actuator-autoconfigure/src/main/java/org/springframework/boot/actuate/autoconfigure/metrics/MetricsProperties.java
@@ -277,21 +277,21 @@ public static class Distribution {
 		/**
 		 * Specific service-level objective boundaries for meter IDs starting with the
 		 * specified name. The longest match wins. Counters will be published for each
-		 * specified boundary. Values can be specified as a long or as a Duration value
+		 * specified boundary. Values can be specified as a double or as a Duration value
 		 * (for timer meters, defaulting to ms if no unit specified).
 		 */
 		private final Map<String, ServiceLevelObjectiveBoundary[]> slo = new LinkedHashMap<>();
 
 		/**
 		 * Minimum value that meter IDs starting with the specified name are expected to
-		 * observe. The longest match wins. Values can be specified as a long or as a
+		 * observe. The longest match wins. Values can be specified as a double or as a
 		 * Duration value (for timer meters, defaulting to ms if no unit specified).
 		 */
 		private final Map<String, String> minimumExpectedValue = new LinkedHashMap<>();
 
 		/**
 		 * Maximum value that meter IDs starting with the specified name are expected to
-		 * observe. The longest match wins. Values can be specified as a long or as a
+		 * observe. The longest match wins. Values can be specified as a double or as a
 		 * Duration value (for timer meters, defaulting to ms if no unit specified).
 		 */
 		private final Map<String, String> maximumExpectedValue = new LinkedHashMap<>();
diff --git a/spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/metrics/ServiceLevelObjectiveBoundaryTests.java b/spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/metrics/ServiceLevelObjectiveBoundaryTests.java
index d5511edf3b0d..8fd5eb246115 100644
--- a/spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/metrics/ServiceLevelObjectiveBoundaryTests.java
+++ b/spring-boot-project/spring-boot-actuator-autoconfigure/src/test/java/org/springframework/boot/actuate/autoconfigure/metrics/ServiceLevelObjectiveBoundaryTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,6 +16,8 @@
 
 package org.springframework.boot.actuate.autoconfigure.metrics;
 
+import java.time.Duration;
+
 import io.micrometer.core.instrument.Meter.Type;
 import org.junit.jupiter.api.Test;
 
@@ -42,11 +44,17 @@ void getValueForTimerWhenFromNumberStringShouldMsToNanosValue() {
 	}
 
 	@Test
-	void getValueForTimerWhenFromDurationStringShouldReturnDurationNanos() {
+	void getValueForTimerWhenFromMillisecondDurationStringShouldReturnDurationNanos() {
 		ServiceLevelObjectiveBoundary slo = ServiceLevelObjectiveBoundary.valueOf("123ms");
 		assertThat(slo.getValue(Type.TIMER)).isEqualTo(123000000);
 	}
 
+	@Test
+	void getValueForTimerWhenFromDaysDurationStringShouldReturnDurationNanos() {
+		ServiceLevelObjectiveBoundary slo = ServiceLevelObjectiveBoundary.valueOf("1d");
+		assertThat(slo.getValue(Type.TIMER)).isEqualTo(Duration.ofDays(1).toNanos());
+	}
+
 	@Test
 	void getValueForDistributionSummaryWhenFromDoubleShouldReturnDoubleValue() {
 		ServiceLevelObjectiveBoundary slo = ServiceLevelObjectiveBoundary.valueOf(123.42);