Your character will start at level 60. This type of server is common in pre-bc or vanilla realms where the cap level is 60 but you will see also servers with higher patches rising the start point so players will level to max faster.
1.12.1 Instant 60 Classic Vanilla Battlegrounds
3.3.5a Instant 60 Twink Custom Content Battlegrounds
1.12.1 Instant 60 Classic Fun Realm PVP