You collection cutoff defines when Shiptheory tries to book in a shipment with Pallet-Track. If you book in a shipment before the collection cutoff time, then the Shiptheory will attempt to book for collection on the same day. If you book after the collection cutoff time, then the Shiptheory will attempt to book for collection the next day.
The collection cutoff time can be found in your Pallet-Track integration's advanced settings section. It defaults to 17:00 UTC.