RSVP vent

Now I know there are a million posts about this but to be honest I thought it would COMMON SENSE that when someone puts a # in on the rsvp you would automatically know that this means this is the amount of seats reserved in your honor........ obviously not. I would NEVER have the balls to enter my own #. Hey at least call and see if this is a mistake (which it wasnt) but surely dont add on 2 more guests... The nerve of some people.