On springs that I have spring rates from the manufacturers, my calcs based on the measuremens are in the ballpark - often very close.
So I have no reason to suspect these are far off.

As mentioned above, the difference in force between secondary and primary springs is not as great as the difference in spring rates appears.
For example, here's a pair from a semi-generic A1 Cardone rebuild. Who knows what the original application was.
Primary spring 8 lbs/in, 0.72" long
Secondary spring 45 lbs/in, .92 in long.

When the springs are installed, they are stretch to approximately .79"
So here's the force restraining the weight (ignoring the mounting angle which changes as the weights swing out)
Distance - Force Primary - Force Secondary
0.79" - 0.56 lbs - 0 lbs
0.82" - 0.80 lbs -
0.86" - 1.1 lbs -
0.89" - 1.4 lbs
0.95" - 1.8 lbs - 1.4 lbs
1.00" - 2.2 lbs - 3.6 lbs
1.05" - 2.6 lbs - 5.7 lbs


All this only goes so far. What we really want to know is what happens when we spin the distributor up!
But it does save some time when looking at which spring is most likely to cause the change in rate or force wanted.