The van der Waals radius of chlorine is 0.175 nm and they use cells with 2 by 3 atoms - two positions for zero and one and one atom wide border as separation to the neighboring cells. This suggests a size of 0.735 nm² per bit or 136 Tbit/cm² which is within a factor of two from the 78 Tbit/cm² from the article and mostly due to the additional spacing between blocks.

They stored 8,128 bits in a plane, the virus contains about 18,400 bits but in a three-dimensional structure. If we could layer this technology - again with one layer for separation - we would get a density of 15.5 billion Tbit/cm³. You could store two years worth of global IP traffic (2015) in one cubic centimeter.