Making Money with Android

I just got an invoice from Startapp!!! WTH

I thought the system works as in put some funds then use it, not spend money and receive a bill!!

Nevermind someone please delete this thread

that’s an invoice, not a bill, it is showing you how much you have spent, the - 64 cents is what you owe, sometimes it takes awhile for ads to shutdown once funds run out.

I guess I misunderstood the word “invoice”
English is not my first langauge, how can I delete this thread?