An up-sell ticket is for a class or activity that requires and additional ticket such as SUP, and AiReal. These tickets can be purchased with or without a festival ticket. Once you purchase your additional classes, the tickets will sync to your profile in about 15 min you will be able to schedule them. A SUP or AiReal class can be scheduled any day of the festival.
If you choose to purchase an up-sell ticket these activities will not count towards your scheduling limit.