hmm, I'm not sure what you mean with that number...
You could wait 30 in-game days to see if the cave respawns with the skooma characters(I did that, they didn't respawn). If you choose to do this(maybe it works for you) DON"T go near/inside the cave for those 30 days, or the timer for respawn will reset.
If you want to advance via console, AND your current objective is " Disrupt the skooma operation" then type this:
SetObjectiveCompleted FreeformRiften01 30 1 then
SetStage FreeformRiften01 40
Another option is to continually resurrect and kill one of the bandits (open the console, click on them*, and run 'ResurrectActor'). I had the same problem, I went there and cleared it out beforehand, so when I had to clear it out for the skooma quest, only two of the enemies respawned (excluding the wolves). It seems the quest tracks the number of people you kill inside the cave during the quest, so there would be enough if you never went there before, but if you previously cleared it out, it doesn't respawn enough enemies to reach the internal counter. I resurrected and killed one of the bandits 4 or 5 times, and it eventually popped up the message that I completed it.
* It can be difficult to click on them, as it seems the dust particles get in the way. It helps if they're up away from the ground and if you can get really close. Once you do click on them, you don't have to click again (the NPC will stay selected when you bring up the console next time to resurrect them again).