I usually shoot Ilford FP4 in 120 format and develop in Perceptol, but last weekend I developed a couple rolls of HP5. Same developer, close to recommended times for development, pretty normal process. There is a large difference in the density of the markings along the edges of these two films (exposure #, film type, etc.). The HP5 is much denser than the FP4. I can't complain about the results of either sets of negatives (I guess that is what matters, isn't it?) but surprised by the text.
I suppose it could be due to the film speed. If the machine that exposes this info is set up to expose at a constant light flux, then a slower film would appear to be exposed less than a faster film. I would think they would either overexpose enough to compensate for this, or adjust for consistent exposure.
I am trying to stick with one film until I feel I can utilize its potential (OK - SOME of its potential) as opposed to trying many types of film, therefore I don't know if this is the case with other types of film. Maybe some of you can take a peek at the markings on your films and let me know.