Onsite works differently than offsite in regards to how many days you could use your tickets at least pre-pandemic.
Others are correct about the timeline talking about offsite. For example if I select February 23rd as my first day for a 3 day ticket it tells me it's valid for any 3 days (doesn't have to be consecutive) between the 23rd and the 27th.
Now as far as calling them Disney does say
"Your tickets are valid for admission to multiple theme parks on any 3 days from Feb 23, 2022 through Feb 27, 2022, subject to park reservation availability. Tickets do not have to be used on consecutive dates. Tickets are nonrefundable.
View Park and Attraction Information After expiration date, the price paid for a wholly unused ticket can be applied to the purchase of a new ticket with an equal or higher price."
In addition to saying:
"You can make changes to your tickets, including your ticket dates, prior to midnight ET of the day before your ticket’s first valid use date, Feb 23, 2022. After your first valid ticket date, you can use the app to add additional days to an eligible ticket or add ticket options. There’s no change fee to modify, but an additional cost applies for dates with higher
ticket prices. No refund or credit is given for changes from dates with higher prices to dates with lower prices. Tickets are nonrefundable, nontransferable and must be used by the same person on all days."
The amount of days you have to use your ticket depends on the amount of days you purchased. Here's a chart from a different thread showing the information:
1-Day Ticket Only the start date selected
2-Day Ticket Any 2 days within 4 days beginning on the start date
3-Day Ticket Any 3 days within 5 days beginning on the start date
4-Day Ticket Any 4 days within 7 days beginning on the start date
5-Day Ticket Any 5 days within 8 days beginning on the start date
6-Day Ticket Any 6 days within 9 days beginning on the start date
7-Day Ticket Any 7 days within 10 days beginning on the start date
8-Day Ticket Any 8 days within 12 days beginning on the start date
9-Day Ticket Any 9 days within 13 days beginning on the start date
10-Day Ticket Any 10 days within 14 days beginning on the start date
This part about ticket expiration debuted in October 2018.
OP did you purchase your tickets through Disney themselves on their website? If so this information is given during the process several times.