Explanation of Strange Radiation Related Units & Shielding
<Variation of radiation intensity with atmospheric g/cm^2
The units refer to mass above unit area. 1030 g/cm2 corresponds to one atmosphere or 14.67 lbs/square inch.
You can estimate shielding effectiveness by multiplying sheilding material density by thickness and check the resulting g/cm2 value versus the table at the link above. This is a rough estimate because it does not take into account secondary particle radiation which varies with elemental composition. It is also limited to application in Earth orbit in absolute terms, but the principle of relative shielding strength should apply on the Moon or Mars as well.
Regards,
Mark