...347 million died in the days leading to chaos day. Anyone can clarify?
The vast majority of those actually died after
Chaos Day/Election Day, as shown in 'The Days After', although the transmission of the Chaos virus between blocks took place during the rioting and fighting prior to the day itself.
But yeah, only 1 in 8 citizens survived those weeks*. Circumstantial evidence from subsequent stories suggests that the fatalities were unevenly distributed, with individual blocks, areas and maybe even sectors having much higher survival rates**, while the death toll in other areas was total. Certain groups might also be expected to have been less likely to succumb due to precautions or protection, including Justice Dept themselves, the isolated or well-defended rich, and well-organised Citi-Defs or the sharper criminal gangs.
The Judges are engaged in an ongoing programme of 'clearance' and rationalisation, effectively continuing the 'safe blocks' policy from the height of the crisis in moving citizens into densely populated areas. Hence some parts of the city look as bustling as ever, while far greater parts are now deserted wastelands.
*Or just 1 out of 16 of the total population at the start of the 22nd Century. Nice work, Justice Department!
** Otherwise how could various criminal networks we've seen continue to function?