Dick,
Your Mec reloader is no different than mine. Both the powder and shot measure less that specified on bar and loads.
For a shotgun, I don't believe that little is going to mean much. I usually weigh ten loads of powder and then average. If the load is 3-4 grs. light then I will try the next bushing up. So long as it is within a grain or so higher I wouln't worry about it.
You could drive yourself crazy worrying about this.
I have been known to drill a few out to get them closer to a particular powder, but they are marked as such and not to be used for a comparable other load.
The manufactures of these reloaders purposely make the charges light for liability reasons.
The published data is usually for everything being weighed and not dropped , I believe.
