You now have to find out 4 more values in your image.
Back in your image editor, create a selection from the very top left point to the top left point where the design of your product should be located. The width and height of the selection will be the top left position of where the canvas should be located. Remember both values.
Right after, select the area that should be editable by your customers. This will give you the canvas width and canvas height. Remember these both values, too. In the end you should know these 4 values:
- the position from top where the editable canvas area should start
- the position from left where the editable canvas area should start
- the width of the editable canvas area
- the height of the editable canvas area