Is there a difference between purge and "do not delete"? I have selected "do
not purge old files" under Build option.

Why is the "bytes saved" number going backwards as if it is deleting.

I hit cancel once.  A pop-up asked if I wanted to stop download.  I clicked
yes.

You are using terms I do not see in the program.  Where/when is
update/continue showing?
Where/when is pause/resume showing?  I only see "pause transfer" in the menu
under "Mirror".