What's my actual work area? Do machine specs mean anything?

Home the machine. Confirm the display shows X=0 and Y=0 (or very close).

Jog to the rear (Yaxis) until it ALMOST reaches the limit. It may have a mechanical stop. Record that value for “Y”.

Now jog it sideways (Xaxis) until the laser module ALMOST touches the machine frame. Record that value for “X”.

Subtract 5 from the “X” value and enter $130=[new value] in the Console window.
Subtract 5 from the “Y” value and enter $131=[new value] in the Console window.

Make your design box these new sizes and try to Frame.