The syntax for DOS windows is CON:x/y/w/h/title/AUTO/CLOSE/WAIT
see also
https://wiki.amigaos.net/wiki/AmigaDOS_Device_Input_and_Output#CON:/AUTO opens the window only if there is any output.
/CLOSE adds a close gadget to the window
The combination of /AUTO/CLOSE allows the user to close the window at any time. It will open again when there is more output.
/WAIT waits at the end of the script until the user closes the window. Without /WAIT the window disappears immediately when the script ends.
There is no time option. You can only trick it. Which means you can remove /WAIT from the window spec and add a wait instruction to the end of your script.
In the same way x/y/w/h are always absolute coordinates. There is no way to open the window relative to the screen size. All you can do is to adjust the coordinates to your preferred screen size.