What have I done wrong?

[artem]

Welcome to the XWin X Server
Vendor: The Cygwin/X Project
Release: 6.8.1.0-1

Contact: cygwin-xfree@cygwin.com

XWin was started with the following command line:

X :0 -multiwindow -clipboard

ddxProcessArgument - Initializing default screens
winInitializeDefaultScreens - w 1024 h 768
winInitializeDefaultScreens - Returning
_XSERVTransmkdir: Owner of /tmp/.X11-unix should be set to root
winCheckDisplayNumber - Cygwin/X is already running on display 0

Fatal server error:
InitOutput - Duplicate invocation on display number: 0.  Exiting.

winDeinitMultiWindowWM - Noting shutdown in progress