Disk Utility: Restore Failure-Source image needs to be scanned for restore.

Hello guys,

I have a .dmg (source image) that I have created from a DVD by myself (read-only format).
I am trying to restore it to a destination and a Restore Failure notification pops-up as follow:

"Restore Failure
Could not find any scan information. The source image needs to be imagescanned/scanned for restore"

I am quite new to Mac. Half of the time, I don't really know what I am doing - but just relying on the 'Help Menu', some research for guides on the internet and most of all read-on most of the posting here in the Apple Forum for what I want to do or might have encountered. Lastly to hopefully also speak the Mac language. For example - What's a disk image? What a .dmg? What's a source image? and etc. 🙂 ~Lost~

So for this case, I am totally lost as I can't seems to understand what does the Restore Failure notification mean at all as I quote above. What does it mean by the Source image needs to be imagescanned/scanned for restore? What do I do from there? How do I scanned my source image? Is there a steps that I miss out while creating .dmg from the DVD?

Could not find any scan information? What scan information? Where do I go to asked for scan information?

I am so lost that I don't even know the right question to ask or begin with.
I know what I want to do and believe it can be done with Mac. But I just doesn't seems to understand the concept of how it really works yet but to just follow blindly throughout the guides. 🙂

So please help me if possible.

Thank you in advance.

Best Regards,

Jon Gan