TSP problem paper

[mickey]

Hello,
I'm reading a paper on TSP problem and there is a phrase I don't understand; could anyone explain it to me?

xxxx present better solutions for the same cities problem: using 2-opt and Or-opt[15] as the
tour improvement operator leads to a quality of 1.37% above the optimum on the average.

what does "a quality of 1.37% above the optimum on the average" mean? reading it seems not good
http://eprints.kfupm.edu.sa/53088/ ,page 3

thanks,