Would like to see the literature on this cause 7 vs up to 50 sounds hard to measure, especially across time. Like what counts as "learn" in the first place? Can recall it without prompting? Can use it in a sentence when prompted to do so? Organically uses it in a sentence without being prompted to?

I mean, there's this thing that comes up often in language learning practices "spaced repetition", but why would that be needed if you can straightforwardly learn up to 50 words in a day.