You sir, are WRONG!
You have bismerched my honour, and the honour of my family!
*throws gloves at bob*
I demand satisfaction!
And that goes double for you trem!
Being a coward I may have to throw some logic at you in a bid to disorient you while I run away.
a round of sandwhiches involves x number of pieces of bread. the unit in question is the sandwhich its self.
a sandwhich could be a slice of bread folded in half
it could be a bread, a filling then another bread.
it could even involve 3 pieces of bread in what id call "a tripple stack" sandwhich. which would go a slice of bread, filling, slice of bread, filling, slice of bread.
the sandwich might not even involve slices, it could be a baguette or a floury bun.
so in conclusion the round does not relate to the number of slices of bread, considering a sandwhich may not even contain any slices of bread. a round is a sandwhich unit.
If i wanted a baguette or bun (actually called a bap) i'd ask for a baguette or bun (bap), if i wanted something made up of pieces of bread i'd ask for a sandwich.
You're right in a round being a unit, the said posted picture shows 2 sandwiches, lets concentrate on 1. It's made up of 2 halves of a single piece of bread (albeit being fancy diamond cut, however the standard horizontal cut is just the same), these 2 halves put together with filling in between are indeed 1 sandwich or 1 "Round".
Hope this clears up any misunderstanding.