How to calculate Schedule Ship Date and Schedule Arrival Date on the Sales Order Line

How to calculate Schedule Ship Date and Schedule Arrival Date on the Sales Order. We have some items which are planned with some lead times. and we have loaded the transit times based on regions.

so ideally we expect, the SSD + Transit Time = SAD, But at many places, we find some unexpected results. For eg..due to lead times

Is there any SQL which we can utilize to validate the results which we actually get on the Sales Order.