OptiMonk is designed in a way that there are several options for setting to whom and when should the popup be displayed. You can set up the campaign according to:
(a) How many pages have the visitors already opened
(b) For returning or new visitors or both groups
(c) Which page(s) are the visitors trying to leave
(d) Visitors who have not visited a page during the recent period of time
(e) Visitors who have been on the subpage for at least 'X' seconds
(f) Visitors who have spent at least 'X' seconds browsing the website. All of these filters can be easily set up within the campaign settings.
Please note that if you select more than just 1 option, all of the conditions should fulfill in order for the popup to display.