if it's in the middle, u can still add more. the dipstick should read full- ie all the way to the right where the grooves are.
1. be careful not to add too much oil tho. if u'r not sure, then add it til it's just before the right.
2. make sure to wipe the dipstick clean and re-insert it for a measurement each time.
3. the best time to measure oil level is after u've waiting 15 minutes after shutting off the engine.