Tippy, I think you will find that the red postbox is cleared at the time posted on the front of it.

The second pickup is for the items handed over the counter......at least that is the way it works at my local PO.  The truck pulls into the loading dock at the side and takes all the parcels and special services mail....registered, SOD etc.

I doubt that the red box would be cleared a second time so close to the first clearance.

In the Sydney CBD the red boxes are cleared 5 or 6 times a day but the POs themselves do not get as many clearances.