At the moment the passage tells you the amount of words unknown but without knowing the percentage this is not hugely useful.
For example: I can see I have 30 unknown words but without knowing the total numbet of words this could be all of them or just 1%!
It would be useful especially when selecting shared passages to know the percentage known and the total number of words, otherwise it is difficult to select passages at the right level.
Anyway just an idea :)
