I have a Fisher control valve and on the front of the actuator is a table listing "initial spring settings (PSI)" for various valve configurations.  What does this mean? Does this mean that the actuator spring has been tightened to the point where it takes that much pressure to start the actuator moving?

I would say, yes you are correct.
Your valve should have come with a manual, however, I have pasted the Control Valve Handbook address from Fisher Controls, if you would like to read more about it.
http://www.documentation.frco.com/groups/public/documents/book/cvh99.pdf

Other sources refer to this as the "Bench setting"  
This is the preload that you have to put on the spring before the valve is installed so that when it is in service at the specified pressure, it starts to open at 3 psi.  

You probably have an EZ or another unbalanced valve.  The flow comes in under the plug and tries to force the plug to open. 100 psi differential against a 4" plug would make a force of 1256 pounds, and you need another 200 lbf per inch of seat:2513 pounds (total=3769) so in a typical actuator with 150 square inches effective diaphragm you would need a preload of about 25 psi to get class IV shutoff.  It is necessary to have either a HUGE actuator or a substantial spring preload to force the valve closed against the process pressure.  

Balanced valves (e.g.: ED) have substantially lower requirement for spring preload.  

Rotary valves such as Ball valves have almost no process pressure effect on actuator force required.  

Butterfly valves handle high differentials easily when closed, but make an enormous dynamic torque when open as a function of velocity....and velocity is a function of differential pressure. 

The bench set is correctly set on a valve when the actuator is not attached to the valve body.  I would suggest you get a maintenance manual from the Fisher web site to properly follow all the procedures and follow safety requirements.  Benchset that is not set correctly can cause valve leakage (to little spring load lets the line pressure lift the plug in closed postion) or not get full travel from valve (spring goes solid stopping travel).

The bench set is correctly set on a valve when the actuator is not attached to the valve body.  I would suggest you get a maintenance manual from the Fisher web site to properly follow all the procedures and follow safety requirements.  Benchset that is not set correctly can cause valve leakage (to little spring load lets the line pressure lift the plug in closed postion) or not get full travel from valve (spring goes solid stopping travel).

MORE NEWS