image persistence problem on Macbook Pro Retina 15"

Is it a faulty or normal behaviour if we see an image persistence after 5 minutes ( less than 15 minutes "Default setting of Energy Saver while using Power Adapter" to sleep/ turn off the display of Macbook Pro Retina 15 inch)?

Today, the Technical support checked my screen using the gray.html and it did not appear. And She said it is a normal behaviour to have an image persistence, because the retina bla bla bla (i don't remember exactly) and just dont leave the laptop too long.

http://r238.local/display/gray.html

Just now after playing a Chess (appx 30 minutes) , and run that test. The image persistence appeared and I guess I need to make appointment again..

Any solution and suggestion?
or We will stick with what the technical support said "Normal Behaviour" ?