and allow you to combine 2 attributes in one slider - Min/Max slider.
It is useful if you have products with attribute falling under some range, like width from to or weight from to etc. Then you can create 2 attributes like min_weight and max_weight and combine both in one slider of type Min/Max slider.
After creating 2 price type attributes go to MANADEV->Layered navigation Menu and open the one which is going to play Minimum role in the slider or in other words - left range of slider. Set Display option to Min/Max slider and Role in Min/Max Slider set to Minimum value. Save it.
Then open the attribute which is going to play Max role in the slider and set Display option to Min/Max slider and Role in Min/Max Slider set to Maximum value and in Minimum Value Attribute dropdown pair it with Minimum role playing attribute. Save it.