Google's John Mueller posted an excellent example of a case of where a webmaster is nervous about a report in Google Webmaster Tools, when in reality, all is good.
Here is a picture:
The issue is a non-issue, just a reporting change in Google Webmaster Tools where the index status report now breaks down http vs https and subdirectories. In this case, that is what happened.
John Mueller said:
A common reason for the Index Status count to go down at the "update" is that an alternate version of the website is verified in Webmaster Tools. A simple way to double-check that is to do a site:-query for just your domain name (eg https://www.google.com/#q=site:fish.com ), and to see which version is shown. If the www-version is shown, then that's the version where most of your data will be. If you want to be on the safe side, just verify both of them.
That is why Google placed the "update" line there, with more details.
Forum discussion at Google+.