Firstly, I do apologise if I don't get all the terminology correctly but I hope I'm still clear.
We bought a second-hand 18-speed bike that has a front gear system that I've not encountered before. It's called a 'microSHIFT' and it has a gradient whereby the rider needs to twist the shifter several times before a chain is moved onto a higher or a lower chainring. It's not just a matter of shifting from 1 to 2, there's several bars in between.
What is the purpose of this and how is it meant to be used correctly?