It belongs to the domain of the app you are using, which you haven't disclosed to us.

I googled the error and landed on the github page of a Python/C project.

Anyway further search revealed that this seems connected to simulation tasks with ever finer grids of cells.

A grid is said to "converge" if results stay roughly the same even with finer grids. More cells mean more computation needed, something one wants to possibly avoid.

Now if you use a grid which is not mutually prime, you are wasting resources, because you are effectively falling back onto an underlying rougher grid available by dividing both dimensions of the grid by a common factor.

I.o.W. you don't wanna see 3x3 tic-tac-toe effects returning on a 9x9 chessboard.

But if the grid was something like 6x7 or 9x11 it's not possible to have a superimposed rougher grid of the same proportion.*

Disclaimer: I'm new to this field, my explanation comes from pure mathematical intuition.

But hey, it's also totally off topic here anyway, so why not guessing :)

update

*) improved "same proportion"

Context is key. Help us to help you. How do I post a question effectively?.

Also, 1234 and 6900 aren't mutually prime ("coprime"). They're both divisible by 2.
map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]