I need help working out what I should owe

Just been trying to use the calculator to work out how much child maintenance I should be paying but cant work it out right can u help?

I earn £21,500 a year I have a 6 yr old daughter who lives with my ex I have her stay with me every other weekend from fri to sun eve then she goes back home also see her twice in week after work for 2 hours sometimes take her home or somewhere to eat.

Worked it out I have her about 78 nites a year can u help me work out my monthly payments?

Thank you