They only have to pay the extra funds if they wish to convert...

They only have to pay the extra funds if they wish to convert the 75% interest to a 99% interest.

At this point in time HDG have an option to acquire a 75% interest in a potential 1b plus tonnes of coal for the princely sum of $3.5m.

sounds okay to me because if they end up paying for the the other 24% interest then they will have proved up a good size and quality resource and the sp will be multiples of its current value.