Shows the number of days that have passed since the previous visit. This metric relates to the chosen analysis period.
A user visited your website on February 13 and February 14:
If the chosen time period is Feb 13 to Feb 14, the number of days relates to Feb 14. If you look at Feb 14, then one visit occurred one day before (=1) and one on the same day (=0).
If the chosen time period is Feb 13 to Feb 15, the number of days relates to Feb 15. If you look at Feb 15, then one visit occurred two days before (=2), and one visit occurred one day before (=1).
Training chapter Extended user-centric analyses