Well, I was also confused by this. And after seeing your question, I was aware of my mistake.
As English is not my mother tongue, I do not understand the exact meaning of 'toroidal' and 'wrapping'. After consulting the dictionary, I find out that it means something like 'cycle'. If we are at the top of the grid and go further north, we will be at the bottom in the next iteration. And now everything is right for us...
Thank you!