All the adjustable powder measures sold are calbrated for FFg powder, and not FFFg powder. They throw even charges by volume, which is what they are intended to measure. They do not throw powder by weight. The markings on the measures are like the notes for " Dram Equivalents" on modern shot gun shell boxes, and cartridges. The markings merely indicate that the volume show is the equivalence to some measured weight of powder, more or less.
If you want weighed powder charge, weight them on a scale, put them in separate containers, and use them at the bench or in the field. Leave the adjustable or other volume measures at home.
If you ever reloaded using the Lee Loader dippers, you have a better idea about the weight? volume problem. The guy may get weights that are closer to the indicated weight equivalence using a current batch of FFFg, and because it is finer grained, the loads may be more consistent for that particular batch of FFFg. However, a different batch, or even the same batch after the powder has been knocked around in the can, or in a powder horn, producing more " fines ", may not throw such a consistent load at another time. Even the relative humidity can alter the volume of a given powder from day to day.