Что означает параметр "P="?

Use AMVARS to control the use of global and active part design variables. You use design variables to create parametric equations for the dimensions controlling your features and parts.
You also use them in an external spreadsheet to control table driven parts.
With AMVARS you can perform a full search and replace when renaming or deleting active part and global design variables, automatically update a linked PRM or Excel spreadsheet file when saving the drawing file, and move active part design variables to global design variables to use in more than one part. You can also specify feature suppression in an external spreadsheet for table driven parts. In the Model tab, right-click a part icon and choose Design Variables.
In the AMVARS dialog box, non-editable text in the display window is shown in the system color specified for Inactive Title Bar. If you are unable to see the non-editable text (or other data in the display window), use the Control Panel to change the inactive title bar text. Change other system colors for other cells. For example, change window text color to change the text color for editable text.