In Google Analytics, unique events and unique pageviews almost mean the opposite of what they sound like.
The unique events metric doesn’t indicate the number of unique times that an event occurred, but instead the the number of sessions during which this event occurred at least one time. Same thing for unique pageviews: the number of sessions during which the page was viewed at least one time.
It seems like the idea behind these metrics is that sometimes the fact that someone saw a page or completed an event at least once during a visit/session is more important than the number of times that this happened.
For instance, a page gets page value or counts towards a goal funnel the same way whether it was viewed one time or ten times prior to a goal or transaction. Similarly, if you set up an advanced segment based on page or event, the number of times that the page was viewed or event was completed during a session (or across all sessions if you set you advanced segment to User scope) doesn’t matter, as long as this happened at least once.
When you see unique as part of a metric name, think in terms of sessions.