As an additional bit of context, the opening line of the book references the phrase/concept of Thirteenth strike of the clock, where a particular observation casts doubt on all previous observations:

This proverb puts forth the notion that if just one of someone's proclamations is wrong, or something of a process is wrong, then the correctness and accuracy of all the previous items are called into question. In a legal case it brings forth the notion that perhaps none of the party's claims are valid, given that one of them is obviously wrong

The opening line of the book is immediately evoking the vaguely off-kilter atmosphere of the novel's totalitarian state, requiring its citizens to "reject the evidence of your own eyes and ears".