I rather like and use many items of Lee manufacturer. I am a bit disappointed in the loading data book. Not really taking any problems with the 'how to' part, I find their data rather underwhelming. There is a reason.
One notes all Lee dies are intended to be used with the data provided, and the manufacturer's assumption is the user will utilize the dipper measures provided, and further the user may not have access to a scale for further refinements. In using the dippers, I find all dippers deliver less of the referenced powder than advertised. This policy is to insure the information will not cause an overload or - heaven forbid - damage to firearm, brass or shooter. (I cannot really fault that approach.)
The data in the manual (which is gleaned from other testers information) is intended to be used with the dippers, or perhaps the various volume measurements included with the slide measure devices - which are an advanced form of dippers. There is no adjustments for 'between' charge loads.
However, the result is the beginning or very simple reloader can load safe loads without buying any additional 'fancy' equipment; and those loads will fire. But they are are on the lower end of the pressure spectrum.
To go with higher pressure loads (observing the limits of some actions) one must move to adjustable measures of the adjustable volume type, weighed to insure the correct level of powder or weighed charges for each individual round. One the subject of 'action' strength, always check what sort of device AND the barrel length of the testing devise. I find it hard to duplicate velocities on anything if the test information was used on a rifle with a six inch longer barrel.
I currently have Lyman, Speer, Hornady and Hodgdon loading information (books). The current editions. When a new loading edition is issued, I get one of those as well. I have a good pile of older loading manuals as reference as well, keeping in mind powders - like gasoline and automobiles - do slowly change over time. Which is a different lecture. Here endeth the leccion.