Taking norethindrone before vacation

Hi all! I'm taking norethindrone so I don't get my period before I go to Italy, but my FLO app shows both the 15th and the 22nd as possible start times for my period (it says the 22nd is more likely). I got 30 tablets which is enough for 10 days, and it's supposed to be 3 days before my period which would be today assuming it starts the 15th, and I leave on the 17th. If it starts on the 22nd instead would it be fine? I leave on the 26th.