They won't get it. Whatever their exit date, the "irrevocable" language basically means that the ACC owns rights to all of their home games through 2027 (4 more football seasons).
If this is about a damages number, what is the value of FSU's games during that period ? Is it their share under the contract (roughly $140 Million), or is it what they would be paid in the market now? FSU will be in a strange position, arguing that "we're being short-changed under the ACC contract" at the same time they're trying to establish the lowest possible value of their broadcast rights for the purposes of a damages calculation.
Seems that their absolute best case scenario is payment of their share for each of the 4 years.