Be careful, what shows up on the app isn't always what you think it is. I saw what I thought was our remaining days on NE tickets on the app prior to one of our trips, and when i tried to book FPs the days it would let me book did not match up with what the app said. When we got to WDW I stopped at GR and checked, and it turned out that the days we were seeing on the app were actually the Plusses we had left from buying the WPFAM add on to the NE tickets, and not the actual park days we had left! Made no sense to me why that would be what we were seeing, but that's what they said and the numbers/days added up. The best way I know of is to go to GR in person and they can tell you the exact date of each use of the ticket, and I wrote them down. There is also a way to do it from home that involves you emailing them your ticket info and they will get back to you, so I've heard, but I've never done it that way. If you don't need to know the days the ticket was used and just need to know how many park days are left, I agree with the pp to try to make FPs and see when it says you are our of days on a ticket. But that won't work if you also have other tickets or an AP also linked.