what the "mean original quality" and "mean quality" mean in the pdf output of MeanQualityByCycle tools of picard

Question

[zengxi.hada]

Dear all,

I use picard tool MeanQualityByCycle to plot the quality distribution of bases. I wonder what the mean of "cycle", and what the difference of "mean original quality" and "mean quality"? Anyone can help me? Thank you.

Best,
Michael