CCTV backup issue

Hi,

We are using Symantec back up exe 2012. I having an issue regarding the backing of video in my CCTV. We want only to backup the newly captured video, 

But, the Symantec stil copying all video from old to new that's why the duration of backup is more than one day. I already created the incremental policy but still the same.  Let me know if this options is correct