ui range slider

Hello developers, I am using your plugin range slider with contact form 7 and it is working fine you can see here: http://ntierinfotech.com/demo/kanga/,,Only thing I need to fix it I want “Increment and Decrement Buttons” with it to increment the range with the help of clicks on the buttons instead of holding and sliding it,,How can I achieve it??
Thank,
Cheers

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