The amount of
oil that it takes to fill a given engine will vary some based upon where the remote
oil filter is installed and the length and size of cooler lines. There could easily be a quad or more in the lines. You have to just continue to add until you hit the fill mark, just add slowly. Then record the amount you used for future reference.
If you are concerned about running the engine with low
oil as you are determining how much oil to use, you can disconnect the coil, pull the spark plugs to relieve compression and just turn the engine over with the starter until you see oil pressure build up. That way you are circulating oil through the lines and filter with low impact on the engine internals. Just be cautious with the starter and do not run it for long and have someone check the temp to make sure that you are not over heating it.