I'm trying to convert the kmer coverage reported in the headers of my contigs into standard coverage. Velvet's manual says the relation between kmer coverage Ck and standard coverage C is Ck = C * (L - K + 1) / L where L is the read length and k is the chosen kmer length.
However, I tried using this formula to calculate C given Ck for each contig, then calculated the median C, i.e. standard coverage, for all the assembled contigs using my average read length, 240, and my chosen kmer parameter, 69. The result I got, 66, was different than the one reported by velvet in the Log file, 23. Do you know why this might be?