Check the event name. If it's for a "3 Day Pass" each ticket will be valid for all 3 days of the festival. 

Happened the same for the festivals with more days. You need to search the event with multiple-days.

For example:

Wireless Festival Birmingham - Weekend

Formula 1 Dutch Grand Prix 2023 - 3-Day Pass Tickets

Brava Madrid Festival 2023 - 2-Day Pass