Your statement is not a question, so I am not certain of the issue. If you are looking for that dialog box, you can type "MS" (default shortcut) for Mechanical Settings, or you can go to Manage tab » MEP Settings▼Mechanical Settings. If this is not what you are asking, can you please reword your question?
I mean that This field changes What part of the effect.
For example, 5 degrees to 10 degrees will change.
But the connections do not notice the difference.
That determines the angle at which Revit will create Pipe Fittings to account for the change of angle in the Pipe. For example, if the Pipe Connector Tolerance is set to 10°, then Revit will not add fittings to a Pipe that is connected to a piece of equipment at a 6° angle. However, if this connection exceeds 10°, Revit will want to add a straight segment of Pipe from the Connector and add an elbow to account for the angle. See the image below.
This is quoted from Revit 2014 Help:
Pipe Connector Tolerance: specifies the number of degrees by which pipe connectors may deviate from their specified mating angle. The default setting is five degrees.
**NOTE that this does not apply when connecting Pipe segments to each other, only when connecting a Pipe segment to a Pipe Connector belonging to Mechanical Equipment, a Pipe Fitting, etc.