In my father's garden

I called twice and clipped with the mailbox valve. Then I spotted this shrub and blipped it,  before I called my father to inform him I was standing outside his front door. After a few seconds, I heard him inside, getting down the stairs. Obviously, he wasn't expecting me at this time.
When I left after a nice chat and tea, my father explained to me that, when I called him three weeks ago, I made the appointment to come on Saturday 29th. And since I had made it a multiple choice,  he had chosen the 29th.