Printing - Letter vs Letter / ANSI A

The printing options in Dorico are great and wide ranging. However I did notice a
“Letter” size which I am familiar with (8.5"x11") but have also noticed a “Letter / ANSI A” size available. I cannot tell a difference - why the two offerings? Thanks.

These come directly from your printer driver. ANSI A is the same as Letter. ANSI B is Tabloid 11x17.

Thanks, Craig! I just had never seen it before.