If your swim has been uploaded with the wrong pool length you can easily update it to the correct pool length. On the desktop website, click edit on the right hand side of the plot and select "change pool length". On the app, just click the menu button on the bottom right of the screen and tick the correct pool size checkbox. This will reprocess the swim and update all of your statistics.
The reception team set the pool length on the docking station before they give you a band - sometimes it is not updated after the pool length changes.