The answer is understatement because he says that he "does not write all that much." This understatement in his short autobiographical essay adopts the same tone found in "There's a Man in the Habit of Hitting Me on the Head with an Umbrella."
An understatement is a literary device that writers use to make an event seem less important that it appears to be.
In his autobiographical essay, Sorrentino uses an undestatement when he says he was won "some literary awards."
Right before this sentence, Sorrentino explains that his work has been included in anthologies in Spanish, English and other languages and has been translated to twelve different languages.
These are great acomplishments which not all writers are able to achieve; so, by saying that he has "won some literary awards," he is understating his success as a writer.
