I run the preview and get all the out of sync items (a lot - 742).
At this point Total Num = 742, Completed Num = 0 and Filtered Num = 4117 and all items are checked.
If I uncheck a directory of files (so as to not sync them) the numbers change as follows:
Total Num = 737, Completed Num = 82 and Filtered Num = 4107
In case it matters, the directory that was unchecked had 5 files in it in a few sub directories.
The Completed Num is concerning.
The change in Filtered Num, not so concerning, but perhaps worth looking into / explaining.
The change in Total Num seems correct.
In checking an unchecking some things in the Preview window, it seems like Completed Num decreases by 1 when a directory on the source side is NOT on the target side and is unchecked.
When only files that exist on both sides are checked, the Completed Num=0.
BTW, after Filtered Num changes the first time, it did not change again.