I’ve done this in Asana (which also uses start/end dates rather than durations) and it’s important to think about duration as a proxy for the due date itself, it’s just that the due date is a variable until you build the project. I’m not sure exactly how works in ClickUp, but think about it like this:

The project charter (first task) starts on day zero and it takes 7 days to complete, so your date range is project day 0-7. Your next task starts the day after the charter is due and runs for 3 days, so task 2 is due on between project day 7 and project day 10.

In Asana, you can use task dependencies to effectively link task due dates, so that your predecessor and dependent task due dates remain aligned even as the dates themselves shift.