Iowa follows federal guidelines which are as follows:
the maximum part of the aggregate disposable earnings of an individual for any workweek which is subjected to garnishment may not exceed

(1) 25 per centum of his disposable earnings for that week, or
(2) the amount by which his disposable earnings for that week exceed thirty times the Federal minimum hourly wage prescribed by section 206 (a)(1) of title 29 in effect at the time the earnings are payable,
whichever is less. In the case of earnings for any pay period other than a week, the Secretary of Labor shall by regulation prescribe a multiple of the Federal minimum hourly wage equivalent in effect to that set forth in paragraph

What it means is that 25% of DISPOSABLE income is garnished. That is your income after deductions taxes, living expenses and other set expenses, then what ever is left over is considered “disposable income”

You may try for a “deferment” for the time being if you are unemployed or having financial trouble.

Hope this helps answer your question

up 25% of your after tax pay – they have to go to court and win a judgment against you first