Question about keeping Breast milk out for 6 hours?

Ra

I know Breast milk can be left out at room temperature for 6 hours in a bottle. I am Breast feeding and expressing.

I was wondering if my baby drinks some of the bottle but doesn't finish it can I give him the rest say 3 hours later rather than pouring Breast milk down the sink? Or does the 6 hours only count if the bottle hasn't been touched yet.