The DOS correction assumes that the darkest object of a band has 0.01 reflectance. This is, however, not really representative and only applying a linear shift to the data.
source: https://www.sciencedirect.com/science/article/pii/003442579290076V
Others suggest to use the lowest 1% of values in a band. So you first have to find this threshold and then subtract it.
DOS-1 correction requires some more parameters, please have a look here: Landsat image conversion to reflectance and DOS1 atmospheric correction
If you really want to radiometrically calibrate your data to reduce atmospheric effects, you have to apply tools like sen2cor or MAJA