When does the backlog snapshot happen? Is it at 00:00? At the end of the working day?
Explore collects backlog information once a day at 12:00 UTC time.
To see your current backlog, create an Explore query based on the metric # Tickets from the Backlog history dataset at any given date in the past other than today.
For more details on which metrics and attributes you can use to report in Explore, see the article: Backlog history dataset.