the data is a statistical linear relation between the tipping weight and the total weight of the hive. basically with a story and a half hive the linear relation is 2.4 X the tipping weight to obtain the bathroom scale weight. then you would subtract the equipment weight (about 30#) to get to the weight of bees and feed inside the box.
ps.... the pictures were taken at one of my favorite location. the location itself is the very top of what use to be an island and coral outcropping when much of Texas was an inland sea (when dinosaurs roamed the earth). unlike most of the soil in the area this outcropping is a deep deposit of sand.