The number in the green bubble shows only net reputation gain since you last checked. See how it matches the 127 next to the Reputation tab title bottom right of this screenshot:
I go to the rep tab (this counts as checking my rep) and the bubble is still there:
Back to the summary and the bubble has gone (because I haven't gained any rep since I last checked a few seconds ago).
So that number in the green bubble isn't a summary of the reputation over any particular time period, except the period since you last checked the reputation tab. That is the only event the number has a reference to.