The last part of the positioning only doesn't cost AP in certain conditions. It's because it remembers the leftovers of your movement - so if you could move 30m for 4 AP, but you only moved 29.5, you can still move 0.5m for free afterwards. Once you've done that, any further movement will cost at least 1AP (at least that's my understanding of it, I don't want to misinform anyone).
