If you accidentally have 2 entries for 1 swimmer in Swimgen, it's easy to merge them into one. There are two swimmers, one with the correct ID, and one with the old or incorrect ID.
To get started, log in to your account.
Click on "Find a Swimmer", search for the swimmer with the old or incorrect ID.
Click "Merge Swimmer" at the top of the page.
Enter the ID of the swimmer you want to merge this one into, then click "Merge Swimmer".