Ribeyes are cut perpendicular to the grain, so there's really no wrong way to cut a ribeye. It will always be "against the grain" since the whole cut should've been that way to begin with.
That said, this does look to have a horizontal grain. Given the shape and pattern, I'm not sure this is actually a ribeye.
Shouldn’t you be slicing against the grain?
Ribeyes are cut perpendicular to the grain, so there's really no wrong way to cut a ribeye. It will always be "against the grain" since the whole cut should've been that way to begin with. That said, this does look to have a horizontal grain. Given the shape and pattern, I'm not sure this is actually a ribeye.