Does it have a drain plug? My mowers, without drainplugs, will never drain the full amount. Might as well put it on an engine stand and rotate flip tilt as needed over and over and over again. Trust the dipstick. Keep it to the full level. Whether you check it before running, or 5 minutes after mowing the yard, shouldn't be anything to worry about if full. I open the shed, check oil level, and if full, mow the yard.
Last oil change after the yard mow, I flipped it over my drain bucket. Most of the hot oil drained out. So, I put it back on the wheels. Repeated it 3x times. My engine hides oil in the nooks and crannies. I change it often enough not to worry about the few ounces left behind.
Plus, its a never change just add oil type of mower. Hogwash!