Discovery Job Timing

I'm curious to know exactly how the scheduling of Discovery Jobs works, and if it can be predicted when a job will run in a massive environment.

I'm working with a customer that has some 100k Assets just to give an idea of the scale. When we schedule a Discovery Job, be it Account or Asset, we're noticing that the job actually runs much later than it is scheduled. My guess is that it gets queued at the appropriate time, but there are so many jobs in front of it that it can take a few hours before it actually starts.

Is this actually how the scheduling works? The jobs get queued at the scheduled time and just run when they get to the front of the line? Or is there a better way of scheduling so that we actually know when a job will run based on its schedule?