> > > Twenty persons sat down for dinner.
> > > Twenty-one left the dining table.
> > > How come?
>
>
> How about this: one of the twenty people was a woman in the last stages of pregnancy. She unexpectedly went into labor a little early, and there was no time to get her to a hospital, so she ended up giving birth right there at the dining room table...hence, 21 people ended up leaving.
>
> Or: one person stood up to have dinner

That's the one! Mothers and grandmothers often do this in case they have to dash back into the kitchen for more cornbread or okra or buttermilk.
But 21 is a small group to eat at grandma's house.
Howard