Where is the 2?

I checked on Clark one morning while he was on the treadmill doing three miles an hour at a 12% incline. He is usually sweaty when he finishes. He had gone over a mile but has to go two so I left him and went outside for my own walk. When I came back in the house a while later I could hear the treadmill. “He must have gotten off while I was gone and has just gotten back on.” I went in to check. He was up to almost four miles and was dripping wet and telling me he had to go to the “2.” Months ago I put an arrow by the first digit in distance so that he would know when he could press stop. Somehow he had gotten sidetracked and missed the “2” and was still full of hope that he would see it. I wondered how far he would have gone if I had not gone in to check on him again.