For those lucky enough to be really high above the earth, the amount of 'earth' that you can see is equal to 180 degrees minus the angle of the size of the earth.
So if earth subtends an angle of 30 degrees, you are actually seeing 180-30 , = 150 degrees of it.
Even when your earth only subtends an angle of 1 degree, you are still only seeing 179 degrees of it.
.