The standard behaviour in the web app is that turning the page moves all blue words to known. However, I prefer to disable this option and to go through the lesson several times, getting rid of some blue words each time.
This leads to the following behaviour, which is not what I want or expect: When the last blue word on the last page of the lesson is resolved, the lesson is considered completed, and all blue words on previous pages are moved to known.
If it matters, I use Firefox on both Windows and Linux.