Using DOPUS to Sync Obsidian files from iCloud Drive

I have Obsidian files in iCloud Drive in C:
This is synced using DOPUS to a backup folder in G:
My last sync was a few weeks ago.
There are about 880 files.
Today, I ran out of space in C: and so decided to disable iCloud Drive, change the location to a new drive J: and re-enable iCloud Drive. iCloud Drive downloaded all 880 files from iCloud to J:
(I should have synced it using DOPUS before removing the iCloud Drive. I want to kick myself)

Now, when I run my DOPUS to sync, of course, it compared and suggested that it will delete all the files in G: and replace them with the "new" files from J: iCloud Drive.

Before I agree to do it, I'd like to seek clarification - what does the DOPUS sync compare to - is it just Date Modified? Does it compare the size? I am a bit wary in case I have done some changes to my markdown files in G: in the past 1-2 weeks and lose it, as I would think that DOPUS thinks that everything in this new iCloud Drive is new.

Thanks for helping!

It depends on the comparison mode you choose.

The modes are described here:

https://www.gpsoft.com.au/help/opus12/index.html#!Documents/Synchronize.htm

Great tip, @Leo .. Thank you. I have "date (different) or size".
Then, in this case, maybe it would be better for me to choose size as it is, 'almost' like a new sync.