What onelogue said. Drain existing crankcase oil - if the bike's not level when you do that, put the bike level to drain any remaining oil. Then one quart will fill it to where it needs to be. If it only took a fifth of a quart, you haven't drained the existing oil.
Ya it only takes 1 qt. I just pull the drain plug and refill thru the chain tension check hole. I change oil everytime I change engine oil. I haven't even had the clutch adjuster cover off mine yet and I have 19,000 miles on it. Using Harley Syn oil since the first change.