clamp(minimum, preferred, maximum);

In this example, the preferred value is 50%.

On the left 50% of the 400px viewport is 200px, which is less than the 300px minimum value that gets used instead.

On the right, 50% of the 1400px viewport equals 700px, which is greater than the minimum value and lower than the 800px maximum value, so it equates to 700px.