This is a Chemistry symbol. It is used in a balanced symbol
equation and represents 6 carbon dioxide molecules. It is normally
written as just CO2. But in this case, it should be part of a
balanced symbol equation.
When the number of total repetitions, as indicated by explicit
repetitions, subscripts, and/or coefficients when present, of each
distinct atomic symbol is the same on both sides of a chemical
equation, the equation is balanced.