Priority is the order in which visitors are considered for assignment to your active Campaigns. When assigning a visitor to a Campaign, SiteSpect attempts to assign the visitor to the Campaign they are eligible for with the lowest Priority. Priority numbers range from one through nine, for all Campaign types except for Origin Experiments.
For example, a visitor is evaluated first for Priority 1 Campaigns. If the visitor is not eligible for any Priority 1 Campaign, then they are evaluated for Priority 2 Campaigns, and so on. By default, Campaigns (except for Origin Experiments Campaigns) are set to 5. If you want a particular Campaign to have more assignments, set it to 4.
In general, Campaigns with Audiences should have a lower Priority than those without Audiences. This allows SiteSpect to first evaluate visitors for Campaigns that have Audiences. Visitors who are not eligible then spill over to higher priority Campaigns that may be all-inclusive (i.e., have no Audiences).
Priority works the same way for Origin Experiments Campaigns, except that the range of Priorities is from negative nine to negative one (-9 to -1). Campaigns that have a -9 Priority are assigned visitors first; Campaigns that have a -1 Priority are assigned visitors last.