I always use my cutting boards upside down so the lines aren't visible. My brain can't handle lines going every which way. Of course, that doesn't work with the rotating one,but I only use it when squaring up smaller blocks - then I concentrate on my ruler. I think the ruler across the front of my $1 SM cabinet is off, too, but it's okay for estimating.
That's terrible that a mat was so far off.
My rulers are all fine and I have several different brands.