Fridge Storage ?

TnG05

I've seen milk can be stored in the fridge 4-6 days and 8 days.  Does anyone know which is right?

I just realized today that DS won't need the milk I pumped today until Monday since he won't go back to day care until them.  Monday will be day 5 so it will fall into the range but I think I would feel better if it were 8 days instead of 4-6.  I'm also thinking I should store it in the back of the fridge.