Memory capacity for Inspiron M5030

I am trying to find out what the max memory of this unit is. The dell site says 6gb, which is a rather strange number, and I am wondering if that was based on Windows 7 addressability or if it is actually the limit. Some of the aftermarket memory sites indicate the machine can take 8gb, and a call to technical support came away with a 4gb capacity, so I am a bit confused.

So....