Course Delivery Date formula

I have a formula that seems simple, but for some reason it's calculating an extra day. There are three columns and the first is duration in days, the next is delivery date, then the third is the end date. What should be happening is the delivery date should be counted as one day, then the calculations should be added to that.

So in the first row the duration in days is 1, the estimated delivery date is 6/28/2024, so the course end date should be 6/28/2024 which is one day. (it's adding the extra day instead of counting the start date as 1 day.

The next rows are doing the same thing, the bottom row shows a duration of 2 days, so the Estimated Delivery Date is 10/29/2024, and the estimated end date should be 10/30/2024 and not 10/31/2024.

The formula used =[Estimated Course Delivery Date]@row + [Duration (in days)]@row

I've tried a few things but none seem to be working.

Also - Is there a way to have it ignore weekends and only use work days?