Coefficients in a balanced equation may correctly be read as:

1. A balanced equation tells you how much of each species takes part. 2. These coefficients represent the relative numbers of reactants and products. 3. Therefore they may be correctly interpreted as ratios. 4. They are not masses, because different species have different molar masses. _Source: OpenStax Chemistry 2e (CC BY 4.0), Ch 4 'Stoichiometry of Chemical Reactions', sections 4.1-4.5_