I had SculpSure done 4 weeks ago and I'm doing a second treatment next week.

There is no optimal time to wait in between SculpSure treatments to the same area, but I would recommend waiting at least 4 weeks in between sessions.  There is no harm waiting a longer period of time though.  It should be fine to have your second treatment next week (which would be at least 4 weeks after your first session).  

At our center we recommend a 6 weeks interval. Most patients are encouraged to do 2 treatments for optimal results.