Battery charge limit

I am new to Mac, and I am trying to set a battery charge limit in the settings. The problem I am having is when I try to lower the slider for the charge limit, it goes down to 75 percent, 50 percent, 25 percent etc. I want to set the charge limit at 85 or 90 percent, but it makes me move by 25 percent when using the arrow keys to adjust the slider. How do I make it move in smaller incraments?