Engine oil capacity with external filter

[JohnBM]

This is probably a no brainer , with a external AC type oil filter fitted to the grey motor it seems to me that extra oil would be required to fill the canister. ?  If the engine has been running & turned off will the oil return to sump so when you check the level after a few minutes it would appear at the full mark , when in actual fact it’s running a bit low , being the amount that goes in the canister. Cheers John