QTR-Quadtone RIP

GRAY_OVERLAP=percent

With this setting is the grey ink applied first, so that all of the black ink is applied OVER all of 
the grey ink,  or are the grey and black dots put down sporadically so they are "mixed"?  
Perhaps this differs by printer.  I'm on a 7800 with K3 if that helps.

Is anyone using this setting, or is it outdated and a holdover from older inksets?

Thanks.

Josh