1" cutout

First time cutting a 1" thick board.

1. If I specify board thickness first, then add a cut path and drill operation through board (3/16" cutting bit), no problem. If, however, I try to subsequently change board dimensions, I get an error message about cuts to deep. I have to set the virtual board thickness to .93" to get past the error message. Spec on bit is "Max carving depth with this bit is 1 inch."
2. So I back up and leave the board at 1", save and upload the project. Board is placed on a sled with 3/4" base (so total thickness is 1-3/4"). Measures fine. Because of the thickness of board and sled I am prompted to enter project thickness. I enter 1. I get a message that says something like board may be too thin .95/1.00. ?? I take a chance (with $20 mahogany stock) and it machines just fine.

I am confused.