I am afraid the chances don't work like that , when we talk about the 5% success rate for example on the lvl6 box it means everyone that try to enchant such box has a chance of 5% to lend a success and 95% to fail so statistically speaking from 100 people that will try to enchant such box 5 has the chance to win. It is not bound to the boxes number as it is bound to the rate that certain box have to success or fail.
Rates aren't as advertised with Mystery Boxes, here is the real math.
in General Live Discussion
Posted
That is what i am trying to say its more like 5% of all boxes lvl6 in the database to end up being lvl7 so good luck if anyone count it would be otherwise 5% of his 100 boxes will get lvl6.