Confused about app versions, documentation

[fuxoft]

Is this the github page for the following app? https://play.google.com/store/apps/details?id=com.duy.calculator.free

I have downloaded it from the Play Store. it looks like very capable app, but I cannot find any documentation for it in the app itself. And it looks very different from the screenshots here on github. For example the screenshot here shows "Base-N Calculator" option which I cannot find anywhere in the app itself. Have I downloaded the correct version?