That is a key consideration.
If you have something that amounts to 1-2 torso tables in each room, or a static location for the actor to stand in all night (Spidoras, picnic traumas, accident scenes, Frank on a lab slab, Drac in a coffin), multiplied times 10-15 rooms or events, then that's at least 10-30 actors that you need to show up. That can be a problem. If your house requires 20 actors to be effective, and only 10 show up, the technical term for that is "you're screwed". If, however, your house can get by on 5 well placed, well used, well utilized, flexible, multi-room actors, and you have 10 show up, you're in hog heaven. Then it's all gravy.
Don't underestimate the power of this concept. JB's legendary Castle Dragon was 4000 sq ft, and it could get by with only 3 actors on slow nights, and you literally thought you were seeing 10 different actors. And that was without breaking a sweat. I know cuz I worked it. I never had to do a 3 actor night, fortunately, but not only was it very evident from the floorplan how that would work, JB trained us for that, and I often used that principle to play 3 parts myself, all at the same time - two behind the walls and one in view of the patrons in a key room.
Likewise, last year, we were promised we would have twice as many actors as actually showed up, with a whole bus load of 9 drama club kids & teacher not showing up, but fortunately I designed the haunt to run on as few actors as possible, and those kids not showing up ended up being a blessing, not a curse. That would have been $300 extra that we would have had to pay out just to have 9 kids and a teacher in masks lulling about, going "grrr" on occasion, but more likely visiting with each other or off in a corner texting or wandering about. Also, another problem to deal with would have been the fact that they were drama club kids. As one other astute member pointed out, they spend all their time learning how to sing and dance and recite soliloquies, not actually interact with people and scare them. They usually feel naked without their Fourth Wall.
So, as to your original concern, if you design your haunt to need as few actors as possible, say, 5 to get by, then anything more that is a bonus. If you need 5, and 10 show up, your set. If need 20, and 10 show up, you're screwed.
How many did you originally need? And, also, how many non-actor rooms do you have?