...I've got a couple suggestions~
One, can you make it so that so that it's sorted by exact score in each tier?
As an aside I genuinely can't tell how it's actually sorted right now...~

Two, can you add settings that let you input custom score ranges for each tier and adjust the tiers' labels/add more tiers?
I, personally, have some... oddly specific score ranges for what I'd consider tiers...~ And that system of mine also includes S+, A+ and F.