then we get a little shorter bit stream then we encode X so that increases the length of the bit stream a little bit more but let's say by this much then then we encode Z again so so that that increases by a little bit so now we can you can just look at this diagram and see how much how long did this bit stream get what was the net change in the length of this bit screen well we we have to add in these two parts right because the bit stream went right there but but then we also subtract how much well I guess not there but we subtracted