I noticed that if I click on the number between the arrows, then this shows:
I presume the number in maroon is the number of downvotes and green is the number of upvotes. Just looking for a confirmation. Also, where are these updates announced?
You just reached 1000 rep a few hours ago. In the FAQ it is stated that the privilege that comes with it is
Show total up and down vote counts
So you can check the number of up- and downvotes by clicking on the number. You no longer only see the difference of the two. That's all there is to it and your interpretation is perfectly correct.
A detailed explanation of this privilege is here and all the privileges are listed here. The latter page can be accessed by hovering your mouse over your username at the top of any page on the main site and clicking on "privileges" in the popup—note that the privileges listed on the right are all clickable and there you'll find detailed explanations.
Generally speaking, updates are effectuated without much ado here (at least I experienced it this way in the 6 months of being a visitor of this site). There is the Recent feature changes to Stack Exchange thread on meta.SO containing a summary of additions and changes.
However, "updates" that come with reaching a certain reputation threshold are announced by a big fat popup at the top of the screen (at least this always happened to me).