how many girls r in a pledge class?

Depends

Correct me if I'm wrong - mostly its based off of the number that Villanova says you can take. There is a maximum number of girls allowed in a sorority pretty much. Some of it depends on the size of the pledge class that graduated the previous year. Some also depends on the number of juniors/sophomores, but I think that contributes more to how many sophs they will take during recruitment. Usually they take between 40-50+ girls per chapter HOWEVER I have no idea if they are going to be making that number bigger or smaller to accommodate for piphi leaving or if a new chapter is considering colonizing. I'm also pretty sure that number doesnt come out until last minute so villanova makes it bigger or smaller depending on recruitment demand/how many girls dropped out. More girls than you think end up dropping (either didnt think sororities were what they expected or bruised ego) so by the end everyone gets a bid at least (again, not sure how piphi leaving will change this). Occasionally some of the mid and lower sororities will offer bids to girls that dropped recruitment if they missed their max number by a few, but its only to a few people and youre by no means guaranteed to get one if you drop.

most of the numbers generally come from how many girls signed up for recruitment ... looking like small pledge classes this spring

Sadly way less than is typical, keep signing up girls!!!!