Throttle valve working condition &working principle different.

For a throttle valve they have given working condition as:
At 1 bar control pressure the throttle valve should be fully open. At 4 bar control pressure the throttle valve should be completely closed (except for the by-pass hole or holes).
But for the same throttle valve working principle is as explained:
A throttle valve is placed in between the air inlet pipe and the unloader valve. The air net pressure is reduced by a control valve (see Figure 1). The resulting control pressure is fed into the actuating cylinder of the throttle valve.
If the air demand decreases, the net pressure will increase accordingly and the throttle valve will close . This will result in a decrease in absolute pressure at the inlet of the compressor element and consequently in a decrease in air delivery, reducing fluctuations in net pressure.An increase in air demand will result in the same way in an increase in air delivery.
This will result in a net pressure staying within a narrow band.
To protect the compressor element against too high a pressure ratio the throttle valve has one or two by-pass holes to guarantee a minimum airflow. In Table 3 the minimum airflow and corresponding maximum pressure ratio as well as the number and diameter of the by-pass holes are given for some different types of units
Any idea?
As control pressure decreases throttle valve should open considering the working conditions.
But in working principle it seems diffrent.