[Gmsh] What are QBAD QAVG in gmsh optimization output?

[Junhui Liu]

I have seen lines in the optimization output, such as
Info    : Opti : (1905640,303,1204509) =  1.08900E+02 QBAD  1.35795E-02 QAVG  7.01827E-01 ( 240.350 sec)

but not sure of what those numbers are. Would someone please explain the definitions of QBAD and QAVG? 

I found that the QBD numbers can vary if I run gmsh again. 
For example I have also got 
Info    : Opti : (1910160,330,1205796) =  1.08900E+02 QBAD  1.72260E-02 QAVG  7.01838E-01 ( 271.289 sec)

Thanks a lot for the help.

Junhui