CullAi detects similar photos and groups them together based on "Grouping Sensitivity" and "Grouping Time Gap".
Higher sensitivity will group more photos together which could be less similar. Default sensitivity groups similar photos on most occasions, but user can adjust that to get more or less photos grouped together.
Time Gap lets you control maximum time gap between any 2 photos in same group. Basically a maximum window in which photos are evaluated to be similar and grouped. For e.g. Time Gap of 5 mins won't evaluate photos 1 hr apart for similarity check even if they were lot similar.