What is the exact meaning of the number that appears when I hover stats graph at admin’s bar:

For example, right now I can see 9 on one of my sites. And when I click it, I can see following numbers of visits per past days:

• today — 26
• yesterday — 80
• the day before yesterday (April 1st) — 98
• March 31st — 131
• March 30th — 99
• March 29th — 118

and so on — there’s no “nine” among these numbers.

I am asking, because it never shows anything accurate or recognisable for me neither for any day nor for any of my blog network’s sites. And I don’t know how to interpret this number.