I do not understand the question.
WinSCP transfers the file and only if the transfer completed successfully, it will delete the source file. Does this answer your question?

Hi There,

As stated in the title:

How does the get-delete command know files got transferred completely when using FTP? I need to know this because there are lots of small files being generated server side and I need to get all of them always.

Would get -delete be secure enough for this purpose?