- “Review” a new card in a deck with default learning steps “1m 10m”.
That’s it, that’s the moment when the next interval is decided. You didn’t specify the grade (Again/Hard/Good/Easy), but anyway, that’s when the interval length in FSRS-4.5 is determined, the rest is irrelevant. FSRS-5 has some extra formulas for handling same-day reviews, but overall it’s only mildly more accurate than FSRS-4.5. Same-day reviews have a very small impact on long-term memory, this conclusion is based on benchmarking lots of algorithms, not just FSRS.
Basically
FSRS-4.5: use the first review of the day, ignore the rest.
FSRS-5: use the first review of the day using the main formula, use the following same-day reviews via the new formulas.