It is used to define what time you stop dispatching orders on the enabling day. The orders placed after the time would be processed on the next working day at the soonest.
If buyers order before the cut-off time, they will be able to pick up their order at the store the next day. If they order after the cut-off time, the next-day pickup will be disabled. They have to wait for the other longer pickup time. It's calculated by adding the delay days to the minimum pickup date.
Your cut-off time is 08:00 PM. If the customer placed an order at 06:00 PM on the 14th of May, and the minimum pickup date is on the 15th of May, he will be able to pick up the order soonest on the 15th of May. If the customer placed an order at 09:00 PM on the 14th of May, and the delay days is one day, he will be able to pick up the order soonest on the 16th of May.
The cut-off time message is great for the customer experience. It informs him that if he orders before the cut-off time, he will stand a chance of picking up the order promptly, giving him more trust in your site and increasing the chance of a conversion.
The number of days if you want to have more time for preparation, only apply for orders placed after the cut-off time.
Time slots when you are able to offer store pickup.