Why Google refunded 200$ because I missed 5 lines of Code

With the new version purchases where happening daily revenue was growing and it was good, also the App size got reduced to 1.36MB. In order for Google Play to ensure a consistent purchase experience regardless of where the user purchases your product, you must acknowledge all purchases received through the Google Play Billing Library as soon as possible after granting entitlement to the user. So next time you are implementing IN-App purchases in your Android App make sure you acknowledge them.

Source: aswinmohanme.github.io