Comment by Alex-Programs

That isn't terribly far off. I used Anki throughout my A levels, spending about 250 hours on it in total according to its statistics, and had something like 10k cards that I reviewed 50k times.

Now, those cards weren't alone - they were reinforcing content that I'd learnt in lessons. But if they were doing it for 10 minutes a day a few times a day, it seems quite plausible to me.