4012 gray tank vent

I just bought a Cyclone 4012 and there is a vent tube for the kitchen sink gray tank which runs up along side the refridgerator vents but it does not exit through the roof is this a factory mistake or is it not suppose to come up through the roof. There are three vents already on the roof. One is the black tank and the other two share the gray tank for the shower and sink.
 
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