Banks Should Understand Simple Subtraction

For most people negative numbers start when counting backwards from zero. Apparently however my bank has their own counting scheme. Counting backwards from somewhere around $22 is when the numbers go negative for them. So far I've been unable to find any documentation stating that $22 is equal to $0 from my bank. And since I have a "no minimum balance required" account, I know that I'm not being penalized because I'm trying to stretch my money. So why is it that I received overdraft charges for a $5 and two different $2.50 transactions? Those numbers aren't precise, but I rounded up to make my point.

That would put my balance around $12. There were no other charges pending, and I haven't filled up with gas from this account in over 2 weeks, so it wasn't due to any of their pre-auth charges. Basically my bank just decided that $22 would be a good place to rob me of $75 since they charge $25 per overdraft. This isn't the first thing that's indicated their poor system to me, but if I don't get my money back it will be the last.