Hi

I am trying to understand the equation for estimated library size (ELS) implemented in Picard Tools. I am using Heng Li's notes posted here: https://software.broadinstitute.org/gatk/media/docs/Samtools.pdf (page 3) . I can't quite figure out how he does the approximation (highlighted in the attached screen print). It will be great if any one can help/comment.

Screen print: http://tinypic.com/r/hwkh3t/9

Best Regards, Datta.