Administrative Earnings Threshold

Can somebody please set this straight for me, what is AET based on? Is is based on Gross or Net?

My Partner earns £1671.18 before deductions and from what I have read online that would place me on light touch? Am I right in thinking that? I mentioned this to my work coach but he turned around and said that it is based on Net.

Also if I am right how do I get the Job Centre to fix this?

If not fair enough.