Hit cap threshold not working

I am entering a custom threshold for my protection spec BiB of 6% hit cap. Yet when I optimize BiB with this it is still giving me a loadout with 3% hit chance. I don’t want to use myrmidon signet instead of Master Dragonslayer ring. Why is it ignoring my hit chance customization?

Give this guide a read: WoW Classic: Set Custom Stat Thresholds

My guess is that you actually want a threshold of 9%, not 6%.