It is very common to come across web pages with multiple repeating elements in the form of a list or a set of similar items. For example, you may have a "select" button against each flight option in the flight listing page on a travel portal. In this scenario, multiple "select" buttons have similar functional purpose. Also the number of such buttons is variable based on test data or time of test execution.
Your test logic will probably require you to select one of the flights and move on from this page. When setting up identification criterion, we need to be able to mark the "select" button as a "repeat" element and try not to find unique identification criterion. Once you mark an element to be a repeat element, you have a choice to select which instance number of this element you are specifically interested. This can be set at element definition time to something predefined, such as 3rd from last, 7th from first, last etc. Or, alternatively you can also point to a specific instance of the "select" button using a statement in action logic.