They state there are "64 Points Per Cubic MM".
They state the world is "a few cubic kilometers"
Even with the assumption that only 0.1% of world space is filled with voxels, that's 64'000'000'000'000'000 (64 quadrillion) voxels. Each needs at least a position (3 x 4bytes) and a colour (3bytes), = 960'000'000'000'000'000 (960 quadrillion) bytes.
I'm sorry, but even with a compression ratio of 17%, you cannot fit 163 Peta-bytes of information in RAM, let alone on the hard drive.