You export your products and you get an error message like this one:
Duplicate references for these products, Products Identifiers: [2/7, 2/8, 2/9, 2/10, 2/11, 2/12, 3/13, 3/14, 3/15, 4/16, 4/17, 4/18, 4/43, 4/44, 4/45, 5/19, 5/20, 5/21, 7/37, 7/38, 7/39, 8/47, 8/48, 8/49, 8/50, 8/51]
It is a list of product and combination identifiers, in the format 1/2, 1 is the product ID, and 2 the combination one.
Each concerned product is a duplicate, that means that the product reference is present at least twice in the database which is wrong.
Example for duplicate:
You must ensure that each product and each combination has a unique reference as shown on the page: validate your catalog structure.
You can then find a product displayed in this list of identifiers, thanks to its Product ID by searching in your catalog, for example: