i don’t know if it’s an error but, i found out two ways of reading of this kanji in the vocabulary. On WK, you ask to read this word as かず that means " amount ", but you can read it too like すう and that means too "Amount " in prefix (with another meaning : Several). So, wouldn’t be better to be able to tape both answers ?
There are a few entries like that, I think. They drive me crazy, because it doesn’t remind you to put in the other reading, it just calls it wrong. I’m surprised this is the one that catches you. I keep tripping up on 札 being either ふだ or さつ. I know the word, I know the reading, but I don’t know which one you want from me, WK!
I figure the difference is something like I’m not noticing that one is vocabulary and one is some other category.
If the meaning is different with the different reading, it’s not an error. They just don’t have the system enabled to handle that currently.
It’s why, for instance, the forehead meaning and ひたい reading are ignored for the 額 vocab. Synonyms and alternative readings need to apply to all aspects. But ひたい is not an alternative reading for the amount meaning of 額, so they don’t include it.
But i suppose here, you could imply that the first one (Suu) is like something like a quantity where you’re emphasizing and the latter could be just a number without any emphasis. If i were to use it as a noun.
honestly, i didn’t have any difficulties for this kanji… But maybe instinctively i did the good answer every time ! (when i wasn’t mistaking it for “Thanks” xD)