Transition formula stage 1 to stage 2

My baby is 5 months 25 days today. I am feeding NAN Optipro 1 and left with about 1-2 days worth of formula in the tin. Was wondering if I should be getting NAN Optipro 1 or 2 after that? Baby would be around 5 months 28 days max and stage 1 is for 0-6 months while stage 2 is for 6-12 months. TIA!