The CRJ-800 is a internal code for NW for a plane with flaps 8.
NW has a total of 5 internal codes for the CRJ

4 are used for Pinnacle
CRJ 50 seat CRJ
CJ8 50 seat CRJ with flaps 8
CR4 44 seat CRJ
CR8 44 seat CRJ with flaps 8

Mesaba code for the CRJ that is loaded is
CXJ 50 seat CRJ with flaps 8