Field help (DAYLTI_SOH) 

This is the necessary lead-time in number of days to deliver this ship-to customer. It is initialized by the lead-time entered on the customer delivery address. This lead-time will be submitted by default on the order lines corresponding to the delivery address of the order header.

It is used to initialize the shipping date from the requested delivery date. The modification of this lead-time triggers the recalculation of the shipping date based on the requested delivery date.