Add return descriptions

src/libs/NumberUtils.ts

@@ -2,6 +2,8 @@ import CONST from '../CONST';
 
 /**
  * Generates a random positive 64 bit numeric string by randomly generating the left, middle, and right parts and concatenating them. Used to generate client-side ids.
+ *
+ * @returns string representation of a randomly generated 64 bit signed integer
  */
 function rand64(): string {
     // Max 64-bit signed:
@@ -48,6 +50,8 @@ function generateHexadecimalValue(num: number): string {
 /**
  * Generates a random integer between a and b
  * It's and equivalent of _.random(a, b)
+ *
+ * @returns random integer between a and b
  */
 function generateRandomInt(a: number, b: number): number {
     const lower = Math.ceil(Math.min(a, b));