Personnel firms have decent experience predicting the takeup of an offer, so they make predictions about how good the offer needs to be, and they try to get close, within expenses and other considerations.
If Z people take the buyout, then, after the dust settles, you layoff the remaining X-Z people.
So it is unlikely that their target reduction is 25%.
A few months later, I was laid off anyway, with severance nowhere near what either of the two buyout offers had included. I regret passing up the offer because I trusted the company and believed things would get better. I spent several months out of work, burned through my savings, and am still feeling the financial effects today.
That doesn’t tell us what this company’s target is, but a voluntary buyout certainly doesn’t rule out layoffs later. If I were facing that choice again, I’d take the buyout in a heartbeat