I don't think my dipstick is correct on my '51 216. When I suck the filter canister dry during an oil change it takes 6 quarts to top it back up. Every where I look says 5 quarts is correct but no mention about the canister.
Since the oil filters were always an option and often dealer installed, the capacity in the owner's manual or shop manual is for the crankase only. It's normal to have to add another quart or so for the filter cannister.