Duplicate copies everything, instead of only new or changed files

[WE4FM 0]

Retrospect Express instruction manual says “Retrospect will only copy files that are new or have changed; it does not copy every file over again.

 

However, every time we use Duplicate it copies all the files, which really slows down the process.

 

How can we make Duplicate copy only new or changed files?

 

Thank you,

 

Fred