Barca are only paying the release clause now..
If there is any way to prove that they offered Griezman a contract in March, it'll be tapping up.. It isnt allowed. It used to be a big deal 10 years ago. No one seems to care anymore, but it still isnt allowed.
So if Madrid can prove it, Barca are fecked.. Unless they claim they intended to trigger the release clause, which at that time was 200m.
Basically, if Madrid have any proof, they could negotiate up with Barca..
Most likely, nothing happens, it gets settled behind closed doors.