Honestly, being a former server, sounds like everything was prolly put on one seat when the order was originally rang up.
I remember the system we had, if you rang everything up under one seat, I think you could do whole or in half, but to go through and compartmentalize everything at the end would be hell, unless you remembered who exactly had what. And still, that would take time. Not impossible tho. Also may have needed a managers card to do certain things as well.
It’s easier to just establish each invidiual person/seat when you ring it up then combine as needed toward the end.