diff --git a/lib/internal/crypto/random.js b/lib/internal/crypto/random.js
index c67170708b70c6..fe76cf1a69ef43 100644
--- a/lib/internal/crypto/random.js
+++ b/lib/internal/crypto/random.js
@@ -498,6 +498,12 @@ function generatePrimeSync(size, options = kEmptyObject) {
   return job.result(prime);
 }
 
+/**
+ * 48 is the ASCII code for '0', 97 is the ASCII code for 'a'.
+ * @param {number} number An integer between 0 and 15.
+ * @returns {number} corresponding to the ASCII code of the hex representation
+ *                   of the parameter.
+ */
 const numberToHexCharCode = (number) => (number < 10 ? 48 : 87) + number;
 
 /**