Replace “Setting the Monitored Architect’s Oxygen to the percentage of Modules (rounding down) which are either Life Support or Hydroponics” with:

Setting the Monitored Architect’s Oxygen to the percentage of non-empty Squares on their Site (rounding down) which contain either a Life Support Module or a Hydroponics Module. (If there are no non-empty Squares on the site, the Monitored Architect’s Oxygen instead becomes 0%.)

For each Site with no Maintained Modules, set its Architect’s Oxygen to zero per cent.