I noticed that when I click on the check mark in the Android app, the word gets marked as ‘status 4’ but not as ‘known’ (i.e. when I open the same lesson on a computer, the words are just ‘status 4’, not ‘known’).
Also, the app doesn’t seem to know the distinction between known words and ‘status 4’ words at all—all known words are underlined with a dotted line and none of them have the check mark ticked.
You’re right, this is on our list as the API currently doesn’t contain mention of the multiple options for Status 4 words. This should be fixed hopefully in the next couple of weeks!
Cecile, a status 4 word is a word that you have learned, a word that went from status 1 to status 4 as you became more and more familiar with it. Known words include not only your status 4 words, but also words that you met in your reading and did not save because you knew them. This latter group is usually much larger than your status 4 words.
By “Goal Chart” do you mean your Progress Snapshot or the Known Words total? If you move a Status 3 word to Status 4, it will be added to your “Learned LingQs” statistic and will be added to your known words total. A word that is Status 4 has already been added to your known words total.