It’s confusing that grading my knowledge of an item:
don’t know, so-so, got it, too easy
is using the exact same numbers as tones.
The confusion is especially strong when doing tone or pinyin items, especially on a single character, e.g.
林: tone 2 know 3
The old iOS app does it better: knowledge is indicated graphically:
X ≈ ✔ ☺
(see screenshots below. Ok I lied the last one is also a check mark on iOS, but it’s better not to depend on color)
The legacy web app also used numbers. But it’s unnecessary and confusing. Which reminds me of how confusing it was that the same colors were used for tones and for grading 
By the way (sorry too lazy to create separate post), I’d like an option not to have to enter the pinyin using the keyboard. On the iPad web app this pops up the keyboard, slowing me down and blocking half the screen. Anyway I often don’t like typing so I just think of the answer, then grade the item unknown to see the answer, then grade it back to known if I was right.
By the way by the way it’s a pet peeve of mine that tones are so important but so poorly displayed in pinyin. The tone mark is often really hard to see! For learners there should be a special font or an additional graphic display that makes the tone very visible. Tone colors are one solution to this, but not everyone likes them. I would prefer really really big tone marks…
I suggest to add this to Skritter’s would be nice some day list 
