The time window is the temporal parameter of a consistency slice. The time window parameter you specify is the total length of the time window. WinPICS calculates the number of samples on a trace by taking half of the user-specified time gate from above the output time value, and half from below. It also includes the value in the centre of the gate, so the time window will be one time sample longer than the length you specify.
What do you want to do?