There are a few ways that the view counter for specific contacts might go up. They could be viewing it from different devices. Their mail server might be scanning all the images inside the email, or the email might be going through multiple layers of scans, or an overly aggressive spam filter before reaching the recipient. All of this can increase the view count on each step.
We use a single pixel image in emails to track opens, so if the image is reloaded multiple times, it’s going to count as a new open each time.