Also, I think your understanding of negative f is correct, and ties back into the original code for the Grid.
I have a question about this record you posted:
>As an example, we find {2:1:5:2:3:9:2} in row 1, where a=3 and t=2. f=-9, so if we take (-9,0,2), we get {-9:0:6:3:3:9:2}
The a and b records make a c val of 18. When I run the values out, I can't make them match with d and e. Is it possible that there's a bug in your code? Or maybe I'm missing something?