It seems longer than that, but regardless, I don't trust any cruise line's published itineraries. Research is easy, and I wouldn't do anything less before I spend many $1000's.
I have a UK cruise planned in August, and I can assure you I know as much as I can know about those ports, and the odds of actually porting there.
I have seen and read enough about Venice that I would fact-check any cruise line that claims it is literally porting in Venice.
But that's just me.