x_count@techDerivedLayers : formal definition?

Hi,

techDerivedLayers(
( t_derivedLayerName x_derivedLayerNum
( tx_layer1 s_op tx_layer2 )
[ x_count | t_rangeVal ]
[ 'diffNet | 'sameNet ]
[ 'exclusive ]
 )
…
)

x_count The number of times contact must be made between the shapes on the two layers forming the derived layer. Valid Values: Any non-negative integer.

although there is good explanation on various s_op, the document lacks definitions on x_count is reckoned. If we have rect1 on layer1, covering <topleft,bottom right>{{-1,0},{0,-1}}, and rect2 on layer2, covering <topleft,bottom right>{{0,0},{1,-1}}, the two shares an infinitely thin edge. There are lots of trivial cases like this.

So how is the "number of contacts" counted? By counting pieces of mininum area block? Please provide a formal definition.

G