I'm not qualified nor a developer, I can only write my thoughts.
I think that in-app balance and total earnings are different, because in-app counts only the BTT that are correctly assigned to your ID, while total earnings counts all the BTT that your ID has "booked". I understood that BTT speed works like a auction and there is a third actor which assure that payment occurs only if the upload was done. I think some "bookings" fail for whatever reason.
For example, once I saw in earnings-graphic three bars around 80 BTT each, but actually I got only 80 and not 240.
But yes, I agree with you that earnings count should be consistent with in-app balance, spendings and withdraws, because current number is meaningless and irrelevant.