A player can attack a region from multiple locations, thus possibly having a total attack fleet larger than the 32,000 SU limit. (at most, it’s possible to attack a region from 8 sides)
However, on the turn in which the battle is completed, a player must move excess ships to a safe region immediately, or they will be scrapped. This is a Forced Movement. See Timing
* Remember that a fleet cannot arrive at a region above the 32,000 SU limit. Thus a player cannot make a rolling oversized armada. They can however coordinate movements ahead of time to ensure there is SU space at a destination. Excess ships from a battle must move to a safe region. They cannot roll forward into another attack. … If no safe region is available, they run out of supplies and are scrapped.
Please note; that if an enemy has attacked regions around a battle, you may lose ships even if you win because they cannot resupply. Those ships can also not enter a second consecutive battle. They will be scrapped without a fight because their supply line has been cut off.