engine oil capacity

ım new on forums and ı owned my first MB 10 months ago so ım searching to find right things for my cars coz ı dont want to do something wrong.
we just had service yesterday oil,oil filter,air filter etc.ı used Mobil1 new life 0w-40 on my petrol engine.they put 6.5L to engine oil but ı searched it on the internet and says engıne oil capacity is 5.5L.
ıs thıs changes when u change oil filter? or they are doing something wrong?
thanx for answers


