The +X number on top of the Google+ Pages is a combination of engagements with the page's posts and total number of followers/people who have the page in their circles (see here).
It seems to me that the page's +X number has more value than number of followers, it is more like the PTAT number on Facebook which indicates the current activity of the page. PTAT on Facebook is based on weekly reach, whereas G+ page's +X is based on both followers and engagement, the number decreases if you leave the page inactive for a while, but it never gets to zero like Facebook.
I just searched to see what other people are doing about this, and according to this blog many pages are using the page's +X number for their milestones and page goals.
So I wonder what is the right thing to do, should we celebrate page's +X or its followers? also note that we can hide the G+ page's followers by unchecking the option which shows the people who have us in their circles.