Share what made you certain.
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I can think of two reasons:
1. Whenever I'm reading, I ALWAYS check the page when I'm on page 99, 199, 299, etc
2. I have this bee croc charm that I always lose. The first time was when I had just gotten in and put it in my croc. The next day I found the same charm on the floor at my school. Sure enough, the charm was missing from my shoe. i had never worn the crocs to school. Another time, the most significant, I feel, was when I was with my friend at his brother's football game. I noticed the charm just resting on one of the benches(one of the ones with holes in them). It was sitting perfectly in the hole. I didn't even notice the charm was missing until I found it. I had never even sat on the benches.