I just performed my 50 hour oil change, replacing the oil and filter. I used exactly 3.25 quarts (3 quarts, 8 ounces). The dipstick is exactly at the "full" line.
This is the method I used. After draining the old oil and replacing the filter, I filled with 3 quarts, started the engine for a minute or so. Then I added oil and measured until it was almost to the full line on the dipstick, started the engine for another minute, then added until it was right at the full line. Then I rode the tractor around for about 5 minutes, waited 5 minutes after turning off the engine and measured again....it's still at the full line.