conversion from cpm/mg to mg
E. Cpm to fmol/mg:  Enter the specific radioactivity as cpm/fmol, the number of cpm counted, and the protein content of the sample in mg. The result is the number of binding sites in fmol/mg protein.

here is a guide of conversions.

The measure is a relative measure, and it can't be very precise as a discrete measure without knowing the precise measurement conditions, i.e. is it mixed every 5 minutes or every 1 minute, is it dissolved in 1 liter or 100ml? CPM denotes the reactivity and not the weight. You are more likely to get a Mol/L rating associated with a CPM, and two vials with the same CPM rating can have different Mol/L and Mg/L depending on their reactivity. 

So, if your paper gives you a comparative measurement, and if it gives you a specific measurement at some stage you should be able to multiply it and figure out the numbers for the various days.