Check this box to display Cumulative Percentage of Summary versus Cumulative Percentage of Features (genes) plots.
It has been shown that a relatively small number of high expressors can skew the normalization results1.These plots illustrate the relative contribution of the different genes to the total count data and enable you to estimate how much the top expressors are contributing relative the rest of the genes.
Bullard, JH et al.(2010) Evaluation and statistical methods for normalization and differential expression in mRNA-Seq experiments. BMC Bioinformatics 11: 94.