I'm still confused:
1) it's on the right of any current prices in that 1 minute time slot, so it MUST be asks (according to the WTF? info on the graph)
2) it's green, so it MUST be asks decreased ( improves the chance of price going up, according to a comment I saw by the author)
So far so good. That matches what you've said, but:
3) it's positive.
Asks added on the right are red, and above the axis, so I thought asks removed would be green but below the axis.
What would you say the same bar would mean if it was green, at the same price, but below the axis?
Maybe above or below the axis doesn't mean anything then? Is it just used to avoid laying red and green on top of each other whenever possible?
edit: I think maybe genuise has given the least confusing answer so far.