On the facts in your post now - -
nothing
why or how are you speaking to him? he is not STILL doing the work is he?
when was the case? have you got a copy of the CCJ? Did he counter claim? how much did he claim at the time? what did the judge say?
it should look a little like this
https://www.bankruptcyadvice-online.co.uk/ccj.shtml
To the right there is a grid: look at the grid and the numbers
There may just be writing and no numbers
in which case you pay nothing
you only pay what the judge ordered