The yet to be introduced in GMS Maker Skill

so when you apply the graded jewel to the item, it is 100% chance that it would apply the corresponding stats?

yes but the weapon made in the process can be avg below or abv just like a drop.. ex. i make a weap that avg is 50 atk and throw on a high grade diamond the weap ends up with 51 atk how? the weap was 48 (below avg) and then the +3 from the diamond = 51 atk

also you can throw a stimulator into the mix.... so it could be even more atk clean....