Was this working correctly before adding the extension? Or is this a new unit?
Did you originally create the device with the .lbdev file supplied by xTool? I suggest you do so if you haven’t. Then you will need to adjust the size of the laser.
Link to .lbdev file from xTool:
https://support.xtool.com/hc/article_attachments/7316422596247/xTool-D1-V2.lbdev
Link to another user getting extension working correctly with links to instructions about changing workspace area: