Oh umm...
Well the numbers indicate the type of map they are.
As you can see, the top maps would represent the how it would look if you had a right beach side.
The bottom ones show how it would look if there were to be a left beach.
They are all different, but the first of each row (A1,A2,A3,A4,A5,A6.) is the "master". It's the default one, the others are simply alterations of them.
Likewise, all that matters is that you could see which maps are available in-game.