There are a few possible situations.
First, if your scale has more users, or your app has set up multiple users, some other people’s measurements may load to your name. It may also happen when someone is using your scale without your knowledge. It is one case for your app retrieving some unknown measurements.
A second situation is that your app may pick up data from some other scales. It could happen when your app paired with this scale in the past. You don’t use this scale anymore, but you didn’t delete it from your app either. Your app may get data from this scale. To avoid it happening, simply remove these unused scales from your app. You should keep one scale in your app, your own scale.
To delete the unwanted data, please refer to “How can I delete a set of my measurement data?”