Hey Obi554!
I didn't understand exactly what you'e trying either.
When you change the slider, it will adjust its value to the value corresponding to the current position of the slider on the bar in relation to max and min values. So, if you have a slider with min 20, max 100 and step 10, you'll have a slider with 9 possible positions and you can change from each to any other of them. Sliders are not used to increase something step-by-step.
You can force the slider to only go up or down one step at a time, but I wouldn't recommend, since it feels very weird and counter-intuitive. Another option would be to use the slider just as a feedback object, instead of an input object, and control its values with buttons. But, again, I'm not sure what you're trying to acomplish here.
The capx below has both situations I explained above. The first slider let's you change it, but limits the change to one step up or down. The second one doesn't let you interact directly with it, but, instead, is controled by the buttons.
https://www.dropbox.com/s/2ej7ti9kb9phh ... .capx?dl=0
Hope this helps. Cheers!