There's nothing that uses just the GstInput.MouseSensitivityVehicle value, so it's not something that is calculated. In your case you should use the max value of 1.5 to get most of the vehicle sensitivity within range. But they are vastly different from hipfire, so for instance Transport Vehicles will still be out of range.
https://www.mouse-sensitivity.com/?share=ffbc50a6650be94a924bc8fe6f8b10ab