AMCAS entering semesters Question

[j99]

---

Members don't see this ad.

When I am adding semesters, it seems there are two different listings for the semester system--some with the code S1, S2, etc, and another set with the code 41, 42, etc. But both say First Semester (Fall), Second Semester (spring). If I am on just a typical semester system, which one do I choose? Or should I just be consistent?