SpeedLabelSetter.cs

using UnityEngine;
using UnityEngine.UI;

public class SpeedLabelSetter : MonoBehaviour
{
    private Text _text;
    public int valueIndex = 3;
    private readonly float[] _values = {
        0.7f, 
        0.8f,
        0.9f,
        1.0f,
        1.1f,
        1.2f,
        1.3f
    };

    private void Start()
    {
        _text = gameObject.GetComponent<Text>();
    }

    public void SetValueIncrease()
    {
        valueIndex++;
        if (valueIndex > _values.Length - 1) valueIndex = _values.Length - 1;
        _text.text = _values[valueIndex].ToString("0.0") + "x";
    }
    
    public void SetValueDecrease()
    {
        valueIndex--;
        if (valueIndex < 0) valueIndex = 0;
        _text.text = _values[valueIndex].ToString("0.0") + "x";
    }
}