Pretty simple [y/n] question. I am making a file that the player moves and the enemies move as the player moves using the choice command but the enemies do not go very fast so can I make it wait less then a second before I selects the default choice. Like choice /d Y /t .5
Since they are speaking in full "Seconds", you have to pick an Integer from 0 to 9999; you can't use fractions of a second (they would usually ask for milliseconds in those cases).
But you can use 0 to request no delay, which should make it as fast as possible.
Note: This was checked on Windows 7, your version of Choice.exe may vary. ;)