A1 and A2 are two grades of Almen strip - sometimes referred to as "aero grade" and "auto grade " respectively. Derived Almen intensity is independent of strip grade - but more data scatter occurs with lower grade Almen strips.
SAE J443 clearly states the limits of intensity for which different thicknesses are suitable. At high intensities C strips should be used - at low intensities N strips should be used. The graph markings show the approximate limits for N, A and C strips with A strip values used for clarity of presentation.
I do not know what # min means but it could easily be lbs per minute. Manufacturers are loth to publish information that could be used against them! The greater the HP the more expensive will be the installation. That is why there are limits - equivalent to your "not applicable cases".
Must end this thread now. For more extensive training why not go to an EI Workshop?
