Did you have a ten dollar credit come in? Remember that things done on Saturday are all on Monday's business day. So if you had some refund or something that was pending it may have come in at a later time, but still appeared on the same day. So you had 61 when you checked it on Saturday and then on Monday a 10 dollar credit came in. Then you check it on Wednesday and it shows 71 for the whole day because it is all considered the same day in banking.
You really shouldn't rely on ATM receipts for balances. They are horribly unreliable and it's a lousy way to keep track of how much money you have in your account.
Go into the bank's website and look at your account there to get a more reliable balance.
It's much easier to just call your bank.
They like to confuse you, and see if you really did learn anything in algebra class - LIKE KEEP A PAPER CHECK REGISTER LOG !!