Originally Posted by Al1943

Depending on the year model and the group model all Shimano shifters do not function the same way. What Retro Grouch says is typical for most shimano triple shifters set up on a triple crankset. There are actually 4 main positions plus a soft click for trimming the smallest chainring. Remember that the first position is simply all of the cable out of the shifter, then the "soft" trim position, then three solid clicks. The middle ring has 2 positions and the big ring has the last position. After shifting to the big ring the 3rd position can be used for trimming. This allows 2 positions for each of the 3 chainrings. Shifting from the smallest to the middle normally requires shoving the brake lever to the 3rd main position and then trimming back to the 2nd if the chain is running on the extreme left side of the cassette. Shifting from the middle to the big or big to middle requires only one click.

Some of the earlier triple shifters, especially in the lower groups have only 3 positions.