The duration of the task should be 7 days. No trouble there.

The issue is the "up to 60 days after it's predecessor". By default the task will have an ASAP constraint, and assuming the link relationship is Finish to Start, it will be initially scheduled to start immediately after the predecessor. You can certainly place a deadline or constraint on the task to ensure you are alerted if the task slides past the deadline.

I hope this helps.
Julie