There's the volume of that corridor that is mineralised,...

There's the volume of that corridor that is mineralised, then there's the volume of this mineralised volume that can be estimated to the degrees of confidence required for the JORC estimates.
My understanding is there is not at a certain spatial drilling frequency required as such, it is dictated by the uniformity of the ore at the professional discretion of the authorised Geologist.
Recent drilling includes holes in locations that provide the best bang for buck returns here, as in an extra hole here with expected intercepts would allow for an expansion etc.