In answer to deerstalker.308's original question. The supernumerary coronet ( or burr ) is formed when there is damage to the pedicle and the stem cells there grow to heal it, no scar tissue is formed as velvet originates from here each season. As there is no nerve connection in this case no antler grew. This would be hormonally controlled in future seasons and may even grow velvet and a bizarre rudimentary antler. There are cases of odd shaped ectopic antlers growing from this position, seen mainly in Roe as they carry out marking from this position on their heads
References: Wislocki; Goss ; Rehn initially then Bubenik ; Bubenik and Pavlansky
Here is an example of my own research as to innervation of antlers in Roe which is the same as Red deer, Wapiti and Fallow References Adams ; Woodbury and Haigh
Dissection
Nerves positions marked in red
Xray of head
This head was made available to me by prometheus.