Shifting down is going to a lower gear. So, if you have numbers on your shifter shifting down will be to lower numbers. If you actually look at the rings on your bike, when you shift down on the front you will go from larger chain rings to smaller. This is using the left hand shifter. In contrast, when you shift down to a lower gear on the rear, using your right hand shifter, you will be using larger size cogs. But you still will be shifting down to easier gears and the numbers on your shifting mechanism will be going lower.
So, first gear on the left hand shifter coupled with first gear on the right will be the lowest gear of all. But you will be on the biggest cog on the back and smallest chain ring on the front.



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