Harvard admits 2,000 undergraduates every year, but it's actually a very large school, granting just about 10,000 degrees per year. The annual commencement ceremony in Harvard Yard only goes through the graduates school-by-school; once dismissed all the graduates decamp to school-specific ceremonies all around campus, where they get their names called and walk across the stage to receive the handshake and (empty) envelope. Perhaps more like YC than you think?