When you are synchronizing folders you never did before (or with different parameters), WinSCP cannot estimate the total time, so it shows only the "Start time" and the indefinite (aka "marquee") progress bar.

When you are synchronizing folders you did before already, WinSCP can do some estimation and shows the "Time left" and a real progress bar.

You cannot have both :)

I see two types of "compare" dialogs. I don't know why this one and there is another one.
One time its comparing with percent and a grow bar. Another time its said "Start time" instead "Time left" and bar is animated (loop) not growing.

After this Comparing dialog its jumps directly to download, without percents in comparing. (target is local)

I would prefer a dialog with "Start time" instead a wrong "Time left" and a growing bar related to files counter instead of time? So the bar should always show the correct progress? ;)

There's no way WinSCP can know how long the comparison will take, as it cannot know how many folders and files are there. All it does, is that it remembers, how many folders were there the last time, and the next time it makes assumptions based on that. If number of folders grew significantly since the last synchronization, you get the behavior you have experienced. Does it explain your issue?

Hello,

It showed 100% ready already after half the time.
It was running 3:35 minutes. But after ~2 minutes its showed 100% with full bar und 0 time left. There was still many folders and files to compare, after its showed long time 100%.

And after finished synchronization it showed a longer comparing time. Instead 3:35 its shows 4:43 minutes.