I’ve noticed that on terms I answer correctly to, sometimes my mastery doesn’t move up at all. A lot of words just stay around 25% and will say stayed at the same kana level with an arrow pointing up even though nothing changed or it’ll say nothing at all. None of the types of mastery stats under the overall mastery are 100% so how does this system actually work? I thought the more you answered the question right the more it would go up and the more you got it wrong the more it would go down so what’s happening?
As far as I know, mastery levels are in steps of ~12% increments for words. Only when the quizzed word's mastery crosses an applicable 'step', does the mastery level go up/down.
If you practise the same quiz-item again and again on a given day, the mastery level for it won't go up beyond a point, as the SRS (spaced repitition system) of Renshuu is the overall determiner/limiter of mastery of a quizzed item. This is done to ensure that the learnt item becomes rooted in the long-term memory, and not just a 'done' item over short-term.
That's my 2 cents. May be others will explain it better.
