Key Master shows too high ratings for 12+ dungeons, about 5

Now its look better

Thanks for the report: If you would, in KeyMaster/Libs/Internal/DungeonTools.lua line 407:
fourthAffixValue = 15, -- Value of the third affix

change the value to 10 instead of 15 and see if that corrects it and let us know.

Thanks!

Fixed in version 1.4.6

An update - this is/was a bug in WoW. While we did patch it in 1.4.6 to align with WoW numbers, KM was correct before. 1.4.7 will revert that change when released.
https://us.forums.blizzard.com/en/wow/t/mythic-score-bug-with-xalataths-guild/2170646