Hi,
When a PDF is overwritten (e.g., due to TEX recompilation) and reloaded by Sumatra, the Page: current/total page-number snippet to the top-left does not refresh, staying with the old page numbers, until the snippet is otherwise redrawn.
Sumatra version: v3.4.14177 64-bit Pre-release.
Thanks,
Shlomi
Auto refresh on compilation, has changed a few times and for any fix to be made you need to check against current pre-release 3.4.14221 (portable should be enough to test page numbers) however I suspect its probably no different from 3.4.177, there are AFAIK no tex installs to check against so need your accurate observations/descriptions.
On compiling does the body text change, with the refresh symbol briefly appearing top right? does the page number change if you change page ? if you dont change page does R force a refresh of page number?
I’ve updated to the latest pre-release version 3.4.14221. On TEX recompilation, the refresh symbol briefly appears to the top right, and the body (=PDF contents) changes as one might expect. However, the page number snippet remains unchanged, until page number is changed, or snippet turned off and on again. Forcing refresh with R has no effect – page number snippet is not redrawn as a result.
The above behaviors are identical to what I recall from earlier versions.
Thank you very much for checking, and I suspect the answer will be the same but after compile and the page number not changing does pressing i key report the same wrong page numbers?.
In addition I can think of a scenario where unexpected numbers can arise and that is based on display mode of two pages e.g. book/facing. So again to clarify any secondary effect ensure your also checking in fit single page mode so highlighted like this 
Showed toolbars, placed in Single Page mode. Before recompilation:
A large chunk of my TeX is commented out. Commented it back in, and recompiled:
Note that the total number of pages is calculated correctly, but not reflected in the snippet, to the top-left of the page.
Thanks for report, Opened as issue