I seem to be able to increase my known words count by just repeatedly pressing “k” when I´ve selected a word. In version 4, this would also be done, but it would get corrected once you refreshed or loaded a new page (your known word count would go down again).
I just tested it and it seems to be true though when I refreshed the word count went back down to what I assume (or hope at least) is the correct value.
Yeah, as @ColinJohnstonov wrote, when you refresh the page the Known words counter will update to the correct number.
Ok then it´s not a problem. It had seemed to not go back when I was using it, but I seem to have been mistaken.
I have noticed something irregular. The total known words number shown in the banner at the top does not match the one I get when I look at all time statistics.
The banner says 10853 known words and the stats say 10849. I see the same in German (banner says 54120 known words and the stats say 54118).