The description said "stop when condition is met" This is a false statement than. If condition was not meet than it should not of stop.
Regardless of the description being good or not (I think it's not), it is not incorrect. It will stop when the condition is met, as it says. If you chose to polish 10 times and you get the stat on the 2nd try it will stop there. It does not say in the description that it will keep polishing until
the condition is met! It says that it will stop when it is met.
In fact, if it continued polishing until the condition was met, it would not be doing what the description says!
because then it would be polishing more than 10 times.
What is this ratio of getting it and how slim is it of even getting it?
I can't tell you because I don't have this information. The only thing I can tell is my personal experience: you get "+ 260 attack" and "+ 3000 health" most of the time, like 90%+, then the remaning 5-10% probability is divided for all the other possible stats. So, pretty low chance to get a specific stat basically. I once spent over 6000 diamonds to get the stat I wanted (although I have also gotten it on the first try in a different occasion).