How to convert RS/R0 ratio on MQ303 Sensor?

Hi. I was following the steps for calibrating the Grove sensor (here: Grove - Alcohol Sensor | Seeed Studio Wiki), but i couldn’t find any information about how to convert the ratio (RS/R0), shown on the last step to mg/L. Any ideas ? I’ll appreciate any help.

I’m sorry to tell you that we can’t provide a formula because the relation between ratio and concentration is nonlinear.