Calculating jump time depends on performance of the computer/server. If it's a new sector or old sector that has been taken out of memory it needs to load all of the asteroids/stations/ships/etc into memory before it allows you to jump to the sector.
The multi-threading of Avorion has 3 different types of threads. Generator, Script, and Worker threads. Generator threads are the ones that execute the loading of sectors. There are some guides that have recommendations for threads based on player count and hardware. The one I used is: https://avorion.fandom.com/wiki/Setting_up_a_server