A size of the range is up to the taste of the designer and their abilities. There is no hard and fast rule for the size of the range as it's more of a bell curve sort of thing. A better pilot can deal with a wider range.

WHERE the center of the range is located is a bit easier to figure. It's related to the Tail Volume Coefficient. This is an equation that considers the wing and tail and the tail moment arm. The number that comes out of it is used to find the aircraft's horzontal neutral point and the CG is then chosen to be so much % ahead of that depending on how much stability the disigner desires.

So at first glance 36% may seem like a crash looking for a home but if the model has a large % tail area with a longer moment arm then it's fine. For example I have an RC old timer that has it's CG located at about 60% and it's actually STILL too stable. But I'm too lazy to modify the fuselage to let me put the electric motor battery pack back further. As it is it handles like a Gentle Lady with a heavy nose.