It is a major worry when the arithmetic of the Opposition's finance spokesman goes awry as David Parker's went yesterday.
It was even more galling for Labour MPs that Parker's mathematical blooper came in almost the same breath as his telling Housing Minister Phil Heatley to check his arithmetic before sounding off at Labour.
Heatley had been telling Parliament that Labour's housing policy would require a new house to be completed every hour day and night for seven days a week for the next 10 years. Even then Labour would fall 13,000 short of its 100,000 target of new homes over 10 years.
By Parker's reckoning building houses at that rate would see 613,000 new homes constructed over the next 10 years. Given the last census estimated the total number of dwellings in New Zealand at 1.6 million, Parker's figure might have rung a few alarm bells. It didn't.
He is not the only Labour MP who has had trouble counting the numbers. Sitting in purgatory is one David Cunliffe.
He has been stripped of his portfolios and shunted to the backbenches for his gross disloyalty to David Shearer. However, the Labour leader did not make the mistake of demoting Cunliffe to the bottom of the rankings and a seat in the wilderness on the other side of the passageway to the lobbies. That is martyrdom territory.
Cunliffe has instead been shifted to a seat which is out of direct sight of the Press Gallery. For someone who loves to play to an audience, that is true punishment.
Cunliffe, however, was not performing for anyone yesterday.
He slipped quietly into the House and into his new seat without fuss. He fiddled with his cellphone. He read some documents. When he occasionally raised his head, the look was one of stony-faced indifference to what was happening around him.
That was the case for 40 minutes. Cunliffe then suddenly broke his silence. The House had moved on to a question about job losses. Cunliffe shouted "can't do the numbers" in the direction of Steven Joyce, the Economic Development Minister.
Given Cunliffe had been unable to get the numbers to topple Shearer, it was an odd remark. But it brought the House down. It was his sole contribution - but one seemingly designed to remind his colleagues he is still very much around. As the Prime Minister said, Cunliffe is in the dog house. But there seems to be life in the old dog yet.