On the data anomalies update page Google posted a notice that on February 5th and 8th of this year they made an “internal index updates” for mobile apps only. Google added “these changes do not affect end users so you should see no change on impressions.”

Here is a screen shot:

I asked John Mueller what that means and he said on Twitter, “It’s an internal indexing update for app content, some sites might be seeing a fluctuation in the stats there.”

So I looked at my index status report for the SER App (go download it) and I saw no fluctuations on those dates around indexing:

I do see movement that seem out of the norm on the 18th, plus that blip on the 21st of January that went back to normal days later.

Here is the tweet from John:

Again, I don’t see any changes with my app on those dates but some of you may?

Forum discussion at Twitter.