My advice is that bride should tell groom “hey we need to arrange a time to go talk to your parents about the wedding” and then the couple goes together and talks to the groom’s parents about numbers and what they were thinking. I get that the groom may not be interested in all the details, but this is his wedding and his family too so he needs to step up and have a conversation. I think they’re setting themselves up for unnecessary problems by letting him take such a complete hands off approach.
I also think it’s one thing if one side of the family needs a few more than the other because one side has a little bigger family but it’s nice when things are pretty equal so it doesn’t feel like the marriage is starting off with one family dominating (although sometimes you get the only child of two only children marrying the person with 4 siblings and 25 cousins but that’s a little different than capping numbers so you can have more people while excluding some of their family).
I also think it’s one thing if one side of the family needs a few more than the other because one side has a little bigger family but it’s nice when things are pretty equal so it doesn’t feel like the marriage is starting off with one family dominating (although sometimes you get the only child of two only children marrying the person with 4 siblings and 25 cousins but that’s a little different than capping numbers so you can have more people while excluding some of their family).