Confused on how lessons work

There’s also a script that I use where you can see your current SRS level for each item, it can help in regards of knowing how close you are to reach a new threshold (or when you unluck something new). There’s also one that works the same way but indicates how far each of the kanjis/radicals are progressed at the dashboard.

That, along with the timeline is a good indicator to know when your next rewievs will be available.