Apart from the above being true.... my further understanding of it is that... TO Shift is not required to be inserted (or an absolute must to insert) in new A320s having GPS Primary (Nav Accuracy High) since the GPS already knows where it is and thereby updates it's present position.
If GPS is not "Primary", or in non-GPS aircraft, you insert the TO Shift as a figure in Metres "M"... being the distance from the Departure Runway threshold to the Intersection being used to commence the Take-off roll.
Eg.: if the intersection is 400 metres ahead of the threshold, then insert '400' in "TO Shift [ ]".
Maybe there's a bit more to it than what I've mentioned here (and I will check on it)... but we do always insert the Shift, perhaps more to serve as a reminder during the Take-off briefing that we are doing an intersection take-off?