If a creditor is garnishing your wages for a judgment they have against you, then state exemptions limit the amount that can be garnished from your wages. Additionally, federal law says that the creditor can take no more than 25% of your disposable income, or the amount you earn that is greater than 30 times the federal minimum wage, whichever is less.
For example, if you earn $600/week, 25% of your income is $150. Assuming $7.25 federal minimum wage, this is $7.25*30 = $217.5. Since $600 - $217.5 = $382.5, and $150 is less than $382.5, the creditor can only garnish $150.