Inserting same card with extra files, how does it handle overwriting existing files?

If I continue to photograph on the card after the first backup and I insert it again in the LBB, how does it handle the files relative to the previous existing backup?
Does it ADD the files that are new? if a file changed? Does it overwrite?

It uses the Rsync protocol:

It should only backup new files that have a different file size or modified date.


Thank you very much for this usefull info.
I will test this to be certain.