 The toe-room is smaller, allowing only 16 / 219 = 7.3% overshoot, which is less than the theoretical maximal overshoot of 8.9%.This is why 16 is added to Y′ and why the Y′ coefficients in the basic transform sum to 220 instead of 255.U and V values, which may be positive or negative, are summed with 128 to make them always positive, giving a studio range of 16–240 for U and V. (These ranges are important in video editing and production, since using the wrong range will result either in an image with "clipped" blacks and whites, or a low-contrast image.)