Hmm, I'm not sure as to which classification system you are referring, however I do know that amphetamine comes in two "forms" (isomers); dextro-rotary (right-handed) and levo-rotary (left-handed).

In the case of amphetamine, the two isomers have significantly different effects if consumed alone; dextro-amphetamine is considered the "effective" isomer, while levo-amphetamine is more peripherally active, similar to ephedrine (a chemical precursor of amphetamines).

Dexedrine is made of pure dextro-amphetamine. Adderall happens to be 75% dextro-amphetamine, with the rest composed of the less CNS-active levo-amphetamine.

So, as a rough guess, Adderall should be 75-90% as potent as Dexedrine, but as you have seen, the pure D-isomer forms do effect some people much more strongly.