Since when does Slinda provide contraceptive protection after starting treatment on day 5 of the cycle?

Good morning I take slinda 2.5 weeks with the fact that not on the first day of the period and 5 days after the lady in the pharmacy said that I can take immediately the gynecologist who chose me the tablets did not mention anything except that they should reduce the abundance of menstruation so my question is whether the tablets already protect me from pregnancy or only after the whole package