neoncube I am more interested in the number of mistakes. When I make a mistake on a word, it would be helpful to confirm how many times I made mistakes on that word.
It may be personal preference, but I feel comfortable with numbers. Memrise has "Difficult words" method, and I usually feel to know how many times I made mistakes on those words.
But It is not essential, so if you don't need it, that's alright.