If you’re smart, the most convenient way to learn your mailbox combination is to never learn it. A lot of people just preset their lock to open without turning the dial.
So I had an extra cookie and decided to leave it for one of these people, who probably checks their mailbox more frequently than the rest of the student body who has no idea how to open theirs. Or, they wont check it for months and it will sit in there and get really moldy.
Either way, random stranger, you’re welcome for this stale cookie you’ll probably never eat!