Hi 23ballingtj,

The Mastery System is designed to track your understanding over time, so you will occasionally receive skills you have already mastered in the Mastery Challenge. If you get those questions down, your status on the skill will move from "Mastered" to "Level Two" in order to give you more practice on that skill. So, if you're getting questions wrong on the Mastery Challenges, it is possible for your mastery percentage to go down by 1% or 2% (which is equivalent to losing mastery in a couple of skills).

If you're answering all of the questions right and your percentage is still decreasing, please report the problem via a support ticket so we can look into it.

Hope this helps! Please let me know if you have any further questions!

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