How did the OA CAT percentile on Cracku predictor decrease for slot 2 ?

yes, but according to Maruti Sir's video for slot 2percentile and score will increase but not happened like that

I don't think the scaled score would go down for any of the slots. Even for Slot 1, it would increase by 1-2 marks and for Slot 2 and 3, it would increase by 3-5 marks. We have seen the scenario earlier in CAT 2019 and everyone gets a better scaled score than the raw score. Hope CAT would do the same this year as this year had the most difficult paper.

Even for Slot 3 it has decreased. They have created a scaled score according to the difficulty of the paper.
Hopefully the real cat score does not do the same.