items stay in apprentice for 3 1/2 days, and in guru for 3 weeks. so assuming that you’re doing lessons at a constant pace and don’t make any errors, you’d have about 6 times as many guru items as apprentice items.
as errors are a thing, it’s probably more like 5 times for most people.
but also, it means that if you change your speed it’ll take 3 weeks for this change to be fully reflected in the number of guru items.