Shukhov really sums up the ending best: he says that his day was "almost happy." "Almost" being the key word there. It's not really possible to have an actual "happy" day in a prison camp after all. And the things that make Shukhov happy are kind of pathetic really – he gets some extra food, he scores some tobacco, he avoids getting tossed in the "hole" (the punishment cell). This type of ending actually packs more of an emotional punch than an ending where Shukhov is actually in the hole. It shows us what his definition of "happy" has become, which demonstrates how awful camp life is. This ending also emphasizes how Shukhov is a survivor. His life may massively suck, but he still manages to look on the bright side of things.
The final sentences of the novella really put the whole story in perspective. We learn that this is just one day out of the 3,653 days of Shukhov's prison sentence. It's hard to get your head around, and it's the type of sentence that makes you go back and think about the entire book all over again.