Pumping confusion

Heather
So i am pumping while LO is in daycare. Noticed something weird.
If i pump into medela bottle and it looks like 5 oz. gen intransfer to Lanisoh freezer bag, its more than 5 oz. so how much is it?
Example, the other day inpumped 8 oz in Medela...it equated to 10'oz in Lanisoh. Which is accurate???