I tried to find the math that translated parts per million to the mass in metric tons. It was almost impossible to find when writing my comment. However, I finally found this: one ppm of CO2 is equal to about 7.821 metric tonnes. What I wrote gave the metric tons as well as the parts per million, which would explain everything you would need. With that additional info, you will have a more complete understanding.
Heck, just put any darned numbers you want, ‘cause no one knows what’s right or even relevant about them.