This field type was added to make automations even more powerful. Instead of having to specify when the automation should occur, the duration field is used to provide you with a way to add a delay for the due date field of the automation or any date time field.
As a result, you can decide how much time needs to pass for the automation to be triggered and what is best, the duration field is set using an intuitive expression allowing you to specify it as 1w, 1d, 1h, 1m, 1s.
This field is really smart, f you want to delay an automation for one year and you add 365d (days) it will convert the total of days to 52w 1d (52 weeks plus 1 day) so that you don't have to.
This functionality was only available for Next Steps automations, but in Banyan, you can add delays to all your automations, regardless of the App.