If your car is old and drip oil, you better fill it up all the way and close to the top, but not exceeding it. If your car is fairly new and got no signs of dripping or leaking, you can fill it to the middle between the two dots.
Regularly check the oil condition (color and level), replace if oil getting dark color (clean oil should be light brown) or every 4 to 6 months, depends on driving condition, and refer to the owners manual all the time. Refill and look for leaks if the oil level drops. Happy driving.
I own, operate and maintain my own cars.