What is your interpretation of these advance springs?

I'm gonna say that light spring is a REALLY light spring. Those numbers are probably correct. Why would someone go to all that trouble if they were not accurate? As easy as the slant distributor is to remove and install, throw it in and stick a light on it. But remember, you do not include vacuum advance when timing an engine. Only initial and mechanical. Vacuum just ends up being "whatever it is" on top of mechanical and initial.