carbetapentane citrate dose

Please clarify dosage difference

I have a Respi-tann Pd suspension that lists carbetapentane 7.5 mg/Pseudo 30mg. and a Respi-tann suspension with carbetapentane 20 mg pseudo 30mg. Why are the two different in the carbetapentane? I received both from our pediatrician as a sample, I am questioning the carbetapentane amount. They are from two different pharmacuetical groups. Please clarify this if you can. Thanks, cari