If you tap just once you will be charged € 1.50, the amount for a BIT ticket (valid for a single journey on the metro, even changing between different lines, but without exiting turnstiles and up to 100 minutes from first tap on Atac surface vehicles). If you make more than four taps within 24 hours, at the moment of the fifth tap the "best rate” feature will be activated, it will charge you a 24-hour daily ticket for € 7, which is cheaper than
five BITs (€ 5 x € 1.50 = € 7.50). The 24-hour validity of the ticket will be calculated from the time of the first tap.
Remember, to apply the "best rate" feature all your taps must be made with the same device. For example, if you start your journey with your contactless payment card, you must continue with the same card and you cannot use other NFC devices (smartphones or smartwatches), even if you have charged the same physical card on them. Same thing if your first tap is done with a smartphone or smartwatch.