Is child support really 25% of your income

Is child support 25% of your income? My friend just found out he has a child the child is 12 the mother didn’t tell him about the child until now.

He makes about $10,000 a month so we were looking it up and it says it’s 25% of your income that seems like a lot because then he will owe her $2,500 a month, and $360,000 back owe if the judge makes him pay that as well. the mother had 0 income. This just doesn’t seem fair.

He did ask to do a meet with the child, but the child refused and had no interest in meeting him. (We are pretty sure the mother told the child to do this but don’t know) So this is solely her coming after him for money, because she found out he makes good money.