the cellular genome size of RGD3.0, the organism with a 473 genome, is 531kbp according to the paper. this means that the genome encompasses ~531,000 nucleotides (base-pairs). for reference, the human genome encompasses approximately 3.3-billion base-pairs.
you can download the human genome from here http://hgdownload.soe.ucsc.edu/goldenPath/hg38/bigZips/hg38.... (it is recommended to use ftp, see: http://hgdownload.soe.ucsc.edu/goldenPath/hg38/bigZips/). it is an ~800mb download.
if it takes 800 mb to store 3.3 billion bases, i would assume it takes (531k / 3.3b) * 800 mb = 0.141 mb to store this genome.