Why Do I have multiple dirs in /data/app I noticed that I was short on space so I checked with a disk analyser app. 

I noticed that I have 8 instances of com.google.android.googlequicksearchbox-1 in /data/app and each dir is about 130 MB. 

The number at the end increments. 

Is this 1 app or 8 versions of the same one? 

Can I delete all but one?  Which do I keep?
This is the package name of Google App as explained here What is the APK (and package) name of the Google App?

I am not sure why there should be multiple entries unless the app has been frequently updated and older versions have incremented numbers at end

In any case, you can check which is the latest using any root explorer (I use Solid explorer) to check properties of base.apk retaining the newest one ( which should correspond to the one having -1 at end, that being the package name )