What am I doing wrong?

[Opey]

I can't measure it right now but I'd say 1/8th to 1/4 inch. Probably closer than a quarter inch.

[bigrak]

The easiest way to check your tiller is to look at the marks that the latches make on your serving.

And what do you look for , any mark closer to the center of the rail than the other ? Is anything wrong in that pic? If so the left is closer than the right.
I thought it was the distance differences between string and bumber?

[Opey]

I'm home now and I measured it. Apparently it is some type of optical illusion. To the naked eye it looks way off but when I measure the string distance from where the arm section connects to the rail it is almost perfect!