Board Thread:Question and Answer/@comment-70.70.29.204-20161017232109/@comment-36.84.86.18-20161022053303

This is also applied to ALL box summon. I read this theory a while ago somewhere.

There is a fixed rate for SR or UR card to be summoned (my theory is 3% for SR card and 1% for UR card). You can keep summoning over and over, the rate stays same. Even when there is 2 cards left,the UR rate stays 1%, not 50%, that's why it is VERY NORMAL to get the UR card at the VERY BOTTOM of the box.