This is what I thought. I'm slightly confused as to what they were doing with the bike without this as the other spacer included is 1/2".

alright, so 1/4" is approx 6.35 mm, but I'm finding individual spacers that are 5mm and the Chris King headset spacer kit includes a 6mm spacer (though I'd rather not spend $30 on a single spacer. I imagine 5 would be good enough?