If you access your new Google Search Console report, specifically the Index Coverage report, you will see a notation around July 14 about a “Google Search Update.” It is not about the big core search algorithm update that happened last week; it is about a system change to the reporting within Google Search Console. Google has noted it upgraded the Index Coverage report to a “new, more accurate system.”
I really wish Google hadn’t written “Google Search Update” there because SEOs, webmasters, publishers and site owners are going to be confused about the terminology added to that screen in Google Search Console. This was a reporting update to Google Search Console’s Index Coverage report; this is not about a Google search algorithm update.
Between the dates of July 14 and August 1, 2018, Google said the data in the Index Coverage report “was estimated from the known August 1 values.” This is because Google was unable to record index coverage data between those dates. Google wrote:
The Index Coverage report switched to a new, more accurate system. Because of this, you may see changes in your reported index coverage. This does not reflect any changes in your site, but a more accurate accounting system.
The system switch began on July 14 and finished on August 1, during which [time] we were not able to record index coverage data. Index coverage data between July 14 to August 1 was estimated from the known August 1 values.
Here is a screen shot from one of my sites:
It would be wise to ignore the data between July 14 and August 1, 2018. You also might see some changes in the reporting from before July 14th after August 1 because of how Google now measures and reports on the indexed URLs within Google Search Console. Again, these numbers have nothing to do with the Google search update from last week.