I can't speak for all shops, but we round the oil volume to the next full quart by specification. We would probably charge 7 quarts for a 6.5l system.
In the shop we have the two type of oil we use in a bulk distribution system (we throw no empty cans and small quantities of oil in the landfill) which we use to fill the engine appropriately. We fill to the stick and we charge to the quart by the factory spec.
I would check your oil warm after sitting for a couple minutes (for full draining) and I would remove some oil if it was more than 3/8 inch aove the full mark. Running it overfull around this amount will only cause the oil to be pumped into the breather system and be burned. At higher levels it will get onto the crank and foam and probably come out everywhere.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician