"Calculate" in folder's properties doesn't display the total size on high DPI display

Though it should. The issue has to do with Windows, monitor and scale factor.
I have a 1080p screen with a scale factor of 100% and a 2160p monitor with a scale factor of 150%.
– If WinSCP is on the 2160p and then I open the properties window, the total size is displayed correctly, on both monitors.
– If WinSCP is on the 1080p and then I open the properties window, the total size isn't displayed, on both monitors.

Thanks for your report. Which of the monitors is your primary one?

I have added this issue to the tracker:
https://winscp.net/tracker/1990

I'm sending you an email with a development version of WinSCP to the address you have used to register on this forum.

Sorry for the late response. My main monitor is the 2160p one.
I tested the version you sent me and it seems you solved the issue.
Here are screenshots with what I see with the current version and with the dev version you sent me.

Thanks for your feedback.