2 different garnishments

If I have already a family support garnishment and then I get a second garnishment from a credit card company can they only combined take 25% of each check? Because I think that payroll at my job is taking more than 25% for the second garnishment. So say that I pay $84.37 each check to family support they're going to take an additional 25% for the second garnishment not considering the child support already being taken out. For some reason I thought with the child support and the second garnishment it would be 25% combined can someone please explain? I go to court tomorrow for an undue hardship. I hope the judge will lower it because after they take all of that out I wouldn't have enough for my bills for the month.