The following is from the sticky post at the top of this board titled
Sticky: *UPDATED* Magic Your Way Tickets And Packages FAQ :
Any ticket that you upgrade to must, at a minimum, have the exact same number of days and the same option configuration. That means if you want more days, or to add more options, you may. But you can't take away any options. For example: If you have an unused 4 day Park Hopper Pass, the bare minimum you would be REQUIRED to get would be a 4 day base with park-hopping and non-expiration. If you wanted to get more days, or get the magic plus pack option, you could add those. If you have a 5 day Park Hopper Plus Pass, at a bare minimum, you would be required to upgrade to a 5 day base, with premium and non-expiration options. You could add more days if you wanted to.