The three buttons at the top of the search results serve a dual purpose:
1. They sort your flight options by recommendation score, time to destination, or price.
2. They provide a quick overview of the results in terms of price and flight times. In some cases, you'll notice big differences in prices and flight duration between the different buttons.
Flight duration is calculated as an average per direction for round trip flights, and total flight time for the entire route for multi-destination routes. These times and prices are calculated from the visible results and change when you filter your results.