If a user lands on a category page and is exposed to a Sequence, what happens if a user jumps to other product pages, lands in a particular segment, and returns to said category page with multiple Sequences configured? 

Under Settings you can enable or disable Sequence Lock, which controls how Sequences should behave after a user has already been exposed to one. 

If Sequence lock is enabled, a user would see the Sequence they have already been served for the entire duration of the session. This might reduce product relevance in favor of more traditional user-experience. 

If Sequence Lock is disabled, a user would be able to jump between segments, and be served the most appropriate Sequence mid-session. This might degrade traditional user-experience in favor of increased product relevance.