The screw I believe will allow you to adjust the pressure switch setting on the pump.
However as you have a controller the pump should be stopped by the controller dead ending the pump. the control should stop the pump before the pressure switch. It also sounds like you system is running on low pressure which is a good thing. High pressure in a system leads to a number of problems
I feel you would be better trying to reduce the calibration setting slightly, the ideal is to have the calibration as low as possible
This video may helpchttp://www.youtube.com/watch?v=U_6dPgfBjSI
When you turn off your pole tap the pump will continue to try pump against the restriction, as this happens pressure builds up, It is this pressure build up the control uses to DE the pump.
How long it will take the control to DE the pump will vary system to system.
The higher the calibration setting the longer it takes for the control to DE the pump. When you turn the flow rate down it will also effect the time it takes to DE the pump as it takes longer for sufficient pressure to build up in the line.
I would suggest that when you have a low flow rate that you also turn the calibration down a little. Reducing the calibration will mean the pump DE quicker.
Also have a look at the following article (point 3 ) covers calibration
http://www.springltd.co/node/130