Rotarix: 2-dose series at 2 and 4 months
RotaTeq: 3-dose series at 2, 4, and 6 months
If any dose in the series is either RotaTeq or unknown, default to 3-dose series.

https://www.cdc.gov/vaccines/schedules/downloads/child/0-18yrs-child-combined-schedule.pdf