There does not appear to be a universal definition of "tick". Some vendors seem to include both sides of the trade as separate ticks. What would YOU expect if a resting 10 lot order in the book got taken out by 10 successive 1 lot orders?
a) 10 individual ticks each with size == 1
b) 1 tick with size == 10 or
c) 11 ticks 10x1 and 1x10.
You will find that different data and software vendors treat this case differently. This is why it is so difficult to duplicate somebody else's tick interval chart without also using the same data feed and even trading application. Not to mention the fact that the exchanges themselves change the rules as they go along.
a) 10 individual ticks each with size == 1
b) 1 tick with size == 10 or
c) 11 ticks 10x1 and 1x10.
You will find that different data and software vendors treat this case differently. This is why it is so difficult to duplicate somebody else's tick interval chart without also using the same data feed and even trading application. Not to mention the fact that the exchanges themselves change the rules as they go along.