Great question. I'm surprised they left $200 in your account. Normally they take everything, up to the amount of the judgment. This makes me suspect there is something else going on here, other than a deficiency judgment resulting from the real estate foreclosure, but it is impossible for me to guess.
As a general rule, creditors can pursue multiple garnishments until the full debt is paid. Maybe even a wage garnishment, but that depends a lot upon what state you are in and where you work. Debt collection laws are different from one state to the next. It isn't simple and there are no easy answers.