Thanks everyone - I did request the ITM's for Mary and John, and also these records for a couple of other ancestors I needed to check. What I DID find was that the 'Residence' column was interpreted differently by various offices/officials - another person assisting me confirmed that apparently no guidelines were given out with the forms so local officials made their own interpretation of what was meant … ie, whether this meant time in NZ or time in that place.... specifically that Parish.
So, Beg, your example may not be an error at all.... on one of the ITM's that I requested I found that my ancestor, Rosina, put down a residence of 3 years and I knew she had been in NZ for 17 years. However I was able to track her place of residence and 3 years prior to her new marriage, she moved from Oamaru to Dunedin, lending weight to the fact that at that time, in Dunedin, they were interpreting residence as 'residence in that parish'.
However the ITM remains a great resource, and can obviously add weight to other facts or suppositions. I also found that ordering it from Archway was easy and swift, although it cost money!.
Back to Mary and John - for residence John (aged 23) put 6 months, and Mary 5 months with 'no one to give consent' - aged 18 at the time. I would say my feeling is that they were new immigrants to NZ. With this age for John the John White who was 31 and came from Australia in 1864 may not be my man. John's age on the ITM is in conflict with his death certificate stating that he was 82 years old in 1916 (which is not unusual, conflicts at the death certificate stage). so as for ship..... back to the drawing board! I notice that there are a number of ships to Port Chalmers in the early part of 1865 and there are apparently no passenger lists for them....*sigh*