What's the meaning of 1PIE,2PIE,3PIE,4PIE

hi,I downloaded the NERO cd-dvd speed 4.7.0.0. but I can’t make sense of 1PIE,2PIE,3PIE,4PIE,5PIE in Advanced Disc Quality, what’s the meaning of it?

thx…

Look here and here for explanations.

thanks…