The deraileurs have stops for you to adjust to allow you to stop or limit shifting where you want it to. This is a 9-speed shifter so you can set it up to shift any cassette size 9-speed and down.

 i understand you set the high and low limit at rear der to set the total width the rear der would move , so the chain doesnt come off.

my questions was, its a 9sp shifter, itd click 8 times. you have only 5 cogs. when you shifter all thru all " 8 times" at the shifter. but how is the shifting when everytime you shift ?

 I guess I don't understand your question but there are 5 cogs with limiters set to stop the derailuer from moving past the high and low cog. With the chain on the smallest cog, you click the shifter one time to move the derailuer which in turn, advances the chain to the next cog. 4 clicks from the bottom cog gets the chain to the top cog. Since the derailuer is limited to move up anymore, the shifter does not click anymore because you can't pull the cable any more. So 4 clicks down and the derailuer puts the chain onto the smallest cog. The shifter only pulls in or lets out cable at a set amount with each click. I doesn't shorten the amount of cable pull based on the amount of cogs you have. This is why you still have to use cog spacing based on a 9 speed cassette. Another example - right now we have a freebody hub on the TR250 with the tips of the splines messed up. So until I find a replacement freebody hub, I've limited the derailuer from moving onto the smallest cog to avoid additional problems. So effectively turning the 9 speed cassette into an 8 speed and the smallest cog is basically used as a spacer. The shifting doesn't change but now I only get 7 clicks from the bottom to the top and 7 clicks from the top to the second smallest cog.