Why is the app name under /data/app different from that under /data/data? After I installed DiskInfo.apk through adb install DiskInfo.apk, under /data/app, there is an installed apk named: 

me.kuder.diskinfo.pro-1.apk

However, under /data/data, there is a new directory named:

me.kuder.diskinfo.pro

Why is the apk name under /data/app appended with "-1"? 

And why is the name under /data/app different from that under /data/data?
The .apk file can be named whatever you want. It doesn't have to be named even anything related to the application ID.

In this case, what happened is that, when the file was downloaded, there was probably already a me.kuder.diskinfo.pro.apk in the download directory (or perhaps a temp directory), so the OS added "-1" to the filename. The contents, however, weren't changed, so the app still registers itself without the "-1".