Cyclon II minimum current

Hi

I have a cyclone II ep2c5t144c8n chip. The problem is with setting the output current.

When I set it to 4mA on the output I get 16.6mA, and when I set 24mA I get 96mA why?

I can lower this by many things but please tell me why is it this way? Shouldn't it be such current as it is set?

Thanks and best regards.