I've discovered what I think is a slight bug in the go diagram generator. If you request coordinates, and don't give a left edge of the board, the coordinates you get are off by one. For example,
Fixed. Thanks for the report.
Please note that faulty diagrams have not been recreated, so you may encounter wrong coordinates. To fix this, you need to change the diagram (e.g. add a letter,) save, edit again and undo your change and save again.
I will probably recreate all 34000+ diagrams of SL within the next month.