WinSCP always uses 1024 not 1000.
In the past, WinSCP used KiB, MiB, etc. units to make it clear. But most people were not familiar with these, so we reverted back to the ambiguous KB, MB, etc.
https://winscp.net/tracker/1123

until hard drive manufacturers inflated disk size by measuring "MB" in 1000 byte increments, kB meant 2^10 and MB meant 2^10 * 2^10 = 2^20. By rights, then, there should be no "MiB" but instead something like "MdB" or "MtB" to indicate 'decimal' or 'base ten' and leave MB to mean 2^20 as before.

Now go ahead and be nit-picky that 1024 should be "kB" and not KB..

Hi, Martin
I have a winscp command console output of a "synchronize" command:

I check the file size in file properties, it is 2,76 MB (2 904 064 bytes On Disk).
Seems when Windows(TM) marks MB(namely 1000*1000 bytes), it is actually MiB(1024*1024 bytes).
Does that mean 2835 KB in output is 2835 KiB actually?

In that sense, for transfer speed "3164,3 KB/s", does "KB" also stand for KiB(1024 bytes) actually?

Thank you!