on interpreting graph based clustering output

hi: I am using cluto from the command line with the following params
Options ------------------------------------------------------------
CLMethod=GRAPH, CRfun=Cut, SimFun=EuclDist, #Clusters: 2
RowModel=None, ColModel=None, GrModel=SY-DIR, NNbrs=10
Colprune=1.00, EdgePrune=-1.00, VtxPrune=-1.00, MinComponent=5
CSType=Best, AggloFrom=8, AggloCRFun=SLINK_W, NTrials=10, NIter=10

I am using a NXN matrix of distances as input. As part of output I get a 2x2 matrix as part of the plotsmatrix switch. It has N entity names on the left hand edge of the matrix and cluster 0 and cluster 1 written on the right edge. And it has red squares marked in various parts of the matrix.

How do I interpret this matrix similarity output?

Can you pl. explain? I read the cluto manual and it isn't in there.

Arjun Khanna.