Slider.minValue

public float minValue ;

Description

The minimum allowed value of the slider.

using UnityEngine;
using System.Collections;
using UnityEngine.UI; // Required when Using UI elements.

public class Example : MonoBehaviour
{
    public Slider mainSlider;

    void Start()
    {
        // Changes the minimum value of the slider to 10;
        mainSlider.minValue = 10;
    }
}