Elihu asks this question to emphasize that Job's sins cannot actually do anything to God. Alternate translation: "If you have sinned, you have not done any harm to God." (See: [[rc://en/ta/man/jit/figs-rquestion]])
Elihu speaks of "transgressions" as if they were objects, and of committing many transgressions as if it were piling those objects one on top of the other. He asks this question to emphasize that Job does nothing to God by his transgressions. Alternate translation: "If you committed a great many transgressions, you still do nothing to him." (See: [[rc://en/ta/man/jit/figs-metaphor]] and [[rc://en/ta/man/jit/figs-rquestion]])