InRegion(3947,276,6196,1267)

Why use a region if you can use a room to define an area on the PCB?

Answer:

Rooms can only be used define an area on the Top or Bottom layers where the components are placed. While InRegion can be used to define an area on any layer of the design.

Key points for using InRegion:

1)  "All coordinates are referenced to the absolute origin (and not to the user origin or component insertion point), and at present, all coordinates always use units of mils. (1 mil = 0.001 inch)"

Syntax:

InRegion(X1 : Distance_String , Y1 : Distance_String , X2 : Distance_String , Y2 : Distance_String) : Boolean

Tip:

Use a temporary Fill to determine coordinates for X1,Y1,X1,X2

Links: 

Can design rule checking be used over a specified area on a circuit board?

No way to write a rule allowing for copper used for logo - Altium Discussion Forums

Reference: InRegion | Online Documentation for Altium Products:

That's it !