yards don't figure scrap content by person, they go by averages, and they're fairly accurate, at least the ones which are still in business. It took me awhile only recently to realize how much my plastics pile was growing, and even though my loads of "tin" were as clean as hek, it finally occurred to me that I was not only selling "tin", but they were paying me for plastic as well, plastic which I had been keeping. If you have some plastics, don't sweat it, unless they recommend you visit the plastic recyclers yard. If you have pure metal, don't sweat it either, plastics don't weigh that much anyway, just be thankful you don't have a pile accumulating at home