Any of the following would be extremely useful:
- Show the “Fixed Start X” and “Fixed Start Y” coordinate on the platform grid.
- Label and mark the coordinates on the grid that is already displayed.
- Allow the user to select the “Fixed Start X” and “Fixed Start Y” by clicking on a point on the grid.
Number 3 sounds like a lot of work, but surely either 1 or 2 would be easy to implement.