When mining commenced, SZ was found to be far more geologically...

When mining commenced, SZ was found to be far more geologically complex than expected and was under-drilled wrt complexity and mineral reserve mining plans. Put on C&M to do substantial infill drilling to work out which parts of the deposit are economically mineable. Unfortunately this will mean that the resources will only convert to reserves over time as mining approaches and they can do the infill drilling. So revised reserves will likely be small initially but production will be continuously replenished in the regular reserve updates. Standard SLR procedure when drilling from surface is too expensive and served SLR well for many years.