Forget the temperature, it has an effect but we are just talking about the spectral distribution graph. All it shows, for any unit of energy, how it (the energy) was distributed in the electromagnetic spectrum. In other words, you have some percentage absorbed in 50-60 micron range, some in 61-70 and so on. If you add it all up, (strictly speaking you need to use integral calculus) you will get the total energy absorbed in all wavelengths which will come to 100%.
This would apply to one gas molecule, or any number.
Clearly, the total absolute amount of energy absorbed will depend on the quantity of gas, or the number of molecules.
BTW if I don't respond sometimes to your direct questions it is due to lack of time, and not because I am ignoring your questions. Cheers.
