Backup size downloaded is in KB's whereas backup is in MB

We have started using URBackup from last 2 months so i am quite new to URBackup.
we had installed URBackup server ver. 2.1.19 and client ver. 2.1.15. Both Server and clients are on Windows platform. We are facing an issue:
On client system when we right click on URBackup icon to access backup from notification area to download backup, the backup size shows 209 MB but when i click “download as zip” the download size is just 4.01 KB. what might be the issue? Please help.
Also, on our storage server where backups are stored .directory_pool folder takes too much space for eg. If the size of backup folder is 200GB(excluding .directory_pool folder) then the directory_pool folder will be around 600GB. Is this normal? if not what can be done in this situation? Can i delete the .directory_pool folder?

Oh! and forgot to tell you that issue still persists even after upgrading server to version 2.2.11 & Client to version 2.2.6