xTool’s firmware is not standard GRBL, and you won’t be able to adjust settings through the Console window.
The dimensions you set in LightBurn will be used by LightBurn, and the dimensions in the firmware will be used by the controller to make sure the commands it’s sent don’t take it outside of its maximum travel limits.
The device profile xTool provides in the below instructions set the dimensions at 430 x 400. Since they’re close to but a bit smaller than the maximum limits set in the firmware, I recommend using those dimensions.
You should also check to make sure your xTool’s firmware is up to date, following these instructions: