As I understand, it is number of post which is in 'review' status, not for your personal, but in total. It is "community's review queue" now.
Previously this notification pertained only to suggested edits, but it
now displays the full count of flags of all kinds (except close votes
on Stack Overflow) that are eligible for review whenever this number ≥
10. This includes flags that I cannot act on personally. I.e., the number reflects the overall community's review queue, not my personal
queue, and will continue to display a number even after I have
completed the maximum number of reviews for a day, or reviewed all
flags that need reviewing. This number is effectively the rest of the
community's job to manage after I've reviewed everything I can for the
day.