Slitherine

Just had a unit of light infantry evade 22 APs. The disrupted bowmen, they started in the village so 3 squares on the diagonal and one square straight. I thought the max was 16+4=20.
What am I missing here ?

I can't explain the mechanics of it, but skirmishers can run a surprisingly long way if they dart through another unit to do it.

They passed through their ally, so maybe they needed less AP. I agree that it's kind of broken though.