>>532392373
600 in a stat will give you a 5% chance at 3* spark
1100 will give you a 10% chance at a 3* spark
however, which stat is chosen to be your blue spark is entirely random so you have a 1/5 chance to get one in the exact stat you want
therefore you must succeed the 20%, then succeed the 5/10%
the way you try to optimize your chances of not getting garbage is thus to raise as many stats to 600 as possible, optimally with one at 1100