The table above is incomplete.
If you fit the GT with 20 or 21 inch rimms, you will have in all 4 corners 255/45R20 or 255/40R21.
Anyhow, it is beyond me why Maserati have 295/40R0 in the back, as logical dimension is 285/40R20 to have the same diameter as the front wheels (255/45R20) and the same diameter of the bach wheel with 19 or 21 inch rimms
If you fit the GT with 20 or 21 inch rimms, you will have in all 4 corners 255/45R20 or 255/40R21.
Anyhow, it is beyond me why Maserati have 295/40R0 in the back, as logical dimension is 285/40R20 to have the same diameter as the front wheels (255/45R20) and the same diameter of the bach wheel with 19 or 21 inch rimms