What is the meaning: The following folders are significantly different. Make sure you have selected the correct folders for synchronization

[mrniqster]

What does this error mean? Here is the rest of the message:

C:\Users\safe\Pictures <->
F:\backup

I am trying to back-up (mirror) my pictures folder on drive C: to backup folder on Drive F:

thank You!

[sloanish]

I believe that this is just a warning that things are not even close to being similar. It is helpful if you try to sync C;\Data\Myfiles to F:\Data\Myfiles\subfiles\ where C;\Data\Myfiles to F:\Data\Myfiles\ is what you really want.
You can ignore and proceed if you wish to.