add comment an answer to a first given question

Author: MaharitB

Sprint-2/2-mandatory-errors/3.js

@@ -7,3 +7,4 @@ const last4Digits = cardNumber.slice(-4);
 // Then run the code and see what error it gives.
 // Consider: Why does it give this error? Is this what I predicted? If not, what's different?
 // Then try updating the expression last4Digits is assigned to, in order to get the correct value
+// the code is not working because the number initialized should be in "" . so it can know is as a string.