Board Thread:General Discussion/@comment-71.238.10.144-20140923102157/@comment-25229582-20140924044804

Summoning drops work like this:

Pretend there are 3 wheels, all with 100 slots. Every time you summon or open a chest, the first wheel spins. 97 of the 100 slots on the first wheel are R cards, 2 are SR, and 1 is UR. If you land on one of the 97 R slots, that is your reward.

The second wheel contains all SR cards and does not spin UNLESS you land on one of the 2 SR slots on the first wheel. Then it spins and whatever it lands on is your reward.

The third wheel contains all UR cards and does not spin UNLESS you land on the only UR slot on the first wheel.

For events like Premium Summon Hyper, the number of SR and UR slots on the first wheel triple. For the current event, only the promotion cards (UR Painter, SR Chronos, etc.) have a 3x appearance rate. This means that the SR and UR slots on the first wheel DO NOT INCREASE. Instead, the slots for the promoted cards increase on the second and third wheels.

tl;dr version:

The actual rate of you getting UR and SR cards doesn't increase at all, but the rate of getting the promotion cards is 3x