Several layers to this answer.
1. Economy Mode generally means that it will run w/o the heater, or it will run to maintain a heat within 30F of the desired temp (ex - you set the tub at 90F and the tub will only kick on to heat when the tub gets below 60F).
2. Virtually all spa pack manufacturers recommend at least 8 hours of filtration per day. That usually is broken into (2) 4 hour cycles
3. The onset of these cycles are typically kicked off with each motor turning on full blast for up to 1 minute.
The reasoning behind this is to clear out the plumbing lines, enact proper filtration, enact proper ozonation, and to allow chemicals to be dispersed. Thus you could have the spa kicking on for any of the above reasons or for the aggregate of the above reasons.
I would suspect that any time the low speed pump is on, the ozone is on.
This is all in generalities so there could be specifics to your situation that are not addressed. I hope this helps. Good luck moving forward.