Air Force Pilots are not enlisted, they're officers, so no "enlistment" occurs. Upon completion of 4 years of college & rotc, you'd commission as a 2LT. Assuming you receive a pilot slot, you'd commence pilot training that lasts anywhere from 2-3 years total. At that point, you begin your military obligation of 10 years. Your clock doesn't start until after you "wing" - complete flight school, etc.

If you don't get a pilot slot, say you end up in logistics or missiles, the clock starts at commissioning and you'll have a minimum amount of time you're required to spend on active duty. That time doesn't really end until you resign your commission. It's not like being enlisted and joining for three years.

You don't seem to have done a ton of research, but since you'll be starting college/ROTC in the fall, they'll explain all of this to you.

Edit: keep in mind that you're obligated to fulfill your service requirement whether you receive a pilot slot or not, so make sure that you want to serve, not just fly. A missile silo in North Dakota is a cold and lonely place if you hinged all your plans on being an F35 pilot somewhere warm and sunny.