When you create a scanning target with a recurring scanning interval. As soon as you finish the configuration of the scanning target, Lansweeper will initiate the first scan.
If you want to set up multiple recurring scans which run at different times, the easiest method is to create a new one every few hours or how much time you want them to be separated by.
Alternatively, you can set a fixed schedule for the scanning targets, once the initial scan has been done, you can edit the targets and switch them over to the recurring schedule.