My bank allows mobile deposit but I think hold money is a weird way can some help me understand this?

So basically you get access to like 200 or so in 800 dollar check and if you get close to zero it give a bit more like 3 dollars into the available section. This is gesa credit union btw. I find this weird and frustrating bc my purchases aren’t really ever below 20 is so dollars so I can’t even spend my money I don’t think at least