Krushert,
Pick upper left corner of grid: Is this very top left A 01?
Yes.
Pick bottom right corner of cell: Is the cell that inserted block resides in?
Bottom right corner of cell A1
Enter # of sub-cells wide (& high): Okay this is throwing me even more.
With the grid posted you'd enter 30 for number of sub-cells wide and 20 for number of sub-cells tall.
Let me know if you need more help.