Does anyone know the numbers?

Quota is still a thing. They take the total number of girls that attended Pref and divide by 11. So to make it easy we say that 1100 signed cards making quota 100 each chapter. But, each chapter had a different number of girls invited - ABC chapter invited 175 but XYZ invited 280. And Panhellenic states that all girls that sign their Pref card maximizing their options will get a bid. The computer matches them up as good as possible filling house ABC with their 100 girls going down to 132 on their list and house XYZ going down to 192 on their list etc., but there are still a bunch left that didn’t match. They hand match the girls that are left and place them into one of her preffed chapters (no, I don’t know how they decide which one); these are called Quota Additions. ABC has fewer Girls left unmatched on their entire list, only 43, but XYZ has 88 left on their list. So when hand-matching goes on, there will be more Quota Additions to XYZ and their new member class will be larger even though they all make the same quota.

This is just an example, so don’t expect an exact statistically accurate depiction. Also remember that there are 11 houses that all have vastly different numbers of girls attending their parties. Every house had girls that attended every single other house on Preference, so that plays into it as well. KD had a girl at DDD who had a girl at AOII who had a girl at PBP, etc.