Free up hard drive space

I don't think anyone can go much cheaper on a system than I did, Sannce 8 channel, but it works. I am curious how to delete files to free up some space on the hard drive, such as me walking back and forth to see if the motion activated record is working, along with other unnecessary video like me coming home from work or working in the garage. The only option I have found in the system settings is to backup the data, nothing about deleting it. Anyone who has worked with a Sannce system knows that the "manual" that comes with it is mediocre at best. Thankfully, from what I can tell, all of the components are pretty universal so I can upgrade piece by piece as money permits and eventually get something that is a little more in depth on its capabilities. Any suggestions for the interim?

Hi. Your system will over write it's self .....there is no option to delete