(To JS/07 M 378 This Marble Monument Is Erected by the State) (epigraph)
There’s no way of knowing what the strange combination of numbers and figures is supposed to mean, but we think it’s a dedication "to" the Unknown Citizen. If so, then Auden is setting up a point he will make in less blunt fashion in the poem: if people are treated only as statistics, they might as well be a statistic, or a number. It’s like calling a person "C3PO" or "R2D2."
He was found by the Bureau of Statistics to be One against whom there was no official complaint, (lines 1-2)
The beginning of the poem sneakily suggests that the Unknown Citizen is, in fact, an individual, or "One." But it also introduces the idea that the "official" realm is all that matters. For example, it makes no difference if there were "unofficial" complaints about him – maybe his wife says he snores too much – as long as the government doesn’t have to deal with it.
Yet he wasn’t a scab or odd in his views (line 9)
A scab is a worker who ruins a labor strike by returning to work before the strike has achieved its goals. Although scabs are usually considered cowardly, at least they take a stand for something, even if it’s their own personal gain. But the Unknown Citizen never breaks from the "mass" identity that binds him in every situation – in this case, at work. There is nothing "odd" about him, but what this really means is there is nothing to him, period. He has no independent personality. He goes whichever way the winds are blowing.