A preview of preview

Love toucan (latest version as of today)...even after my loss but I lost a load of folders recently on a mirror sync.
A read a similar problem in this section but I'll relate this in case it is different. I must point out before I start that that I did not preview the results first, and that maybe I do not understand mirror sync...but if I made the mistake than I am sure others will too. Folder names changed to make it easier, it goes like this.....
Drive C has a folder called Z. Z has lots of subfolders. Having copied Z to an external drive G, I regularly sync update Z to G using Toucan. G has four other folders A, B, C, D.
After a while I decided that I needed a mirror, just to get things exact. I cleared G of the sync update folder Z defragged and was left with A, B, C, D. on the external G drive. I then selected Z from the C drive and told Toucan to mirror it on the G drive. I had 10 gigs of data so left it and came back later. I did not find what I expected. The C drive was fine. The G drive was not. Folders A,B,C,D were not on the G drive and neither was folder Z. Instead the CONTENTS of folder Z, i.e. all its subfolders etc., were on the G drive , but not folder Z itself. I checked the Toucan log. It told me what had happened. When I had highlighted folder Z to mirror to G, toucan had mirrored the CONTENTS of folder Z to G and then removed those things that did not match, namely A,B,C and D. It appeared to have treated drive G as folder Z. Not catastrophic I have backups and unerase tools, but not what I expected. As I said at the start, perhaps I do not fully understand mirror, but if it was my mistake, I think it is an easily made one and maybe something which warrants looking at. Thanks, still loving Toucan though....just not mirroring anymore!