Where does it show how long one has been on a level?

[UInt2048]

And if you have reset, you might go here which lets you show previous attempts at a level:

[Web App] WaniKani History + Timemachine

Wani Kani History Web App This is a third-party script/app and is not created by the WaniKani team. By using this, you understand that it can stop working at any time or be discontinued indefinitely. Due to recent API changes that limit the data retrieval to the API, this website’s functions were severely reduced. Although this change was said to be temporary a restoration date has not been given. Main Link You have to get an API v2 key. You can find it on your dash…