How can create custom thresholds value in my dashboard?

I have created a dashboard that it shows network interface sent Mb/s now I have created a thresholds when traffic is 1-50Mb/s it shows green color
50-80 Mb/s it shows blue color
80-90 Mb/s it shows yellow and more than 90 Mb/s it shows red color

but as you can see now my speed is 20 Mb/s and it shows red color . How can correct it ?

Not sure what is happening there. Can you insert a green color threshold from 1 (keep the Base and 50/blue as they are now).

I changed it such as attached pic but there is not any change .

Have you tried value mapping instead? And are those values really numeric?