User blog comment:Chad Pattan/Dear Nubee: It's Time To Clean Up The Cards./@comment-25474140-20150615063446/@comment-25474140-20150615152730

And to put it simple.

Game first rolls to decide which type of card you get R/SR/UR.

Then it rolls on table of corespodning cards.

That way they can easy tweak the rates of R/SR/UR and they can add/remove new cards from tables.

Look like how often people get event SR compared to other SR from summons. Obviously event SR has higher chance to be rolled with second roll than other SRs in pool.

Changing ammount of Rs wont do anything, the rates itsels are still.. bad.