Centrex/Arrium dual tenancy

I was just over reading one of the latest CXM announcements and saw this....

"Centrex signed a dual tenancy agreement in July 2013 covering the 600m portion of the deposit on Arrium Mining’s (“Arrium”) tenement EL4732. The agreement gave Centrex the right to conduct an 18 month exploration program over the area that commenced in December 2013, during which time Centrex can elect to lodge a Mineral Claim in its own name over the area. Centrex made an initial payment of A$200,000 to Arrium for the right and will pay another A$300,000 on lodging a Mineral Claim. During the dual tenancy if Centrex discovers >1Mt of DSO (>50% Fe) of Cross Section, Arrium may elect to mine this portion of the deposit in its own right or alternatively allow Centrex to mine it for a 5% royalty. All non-DSO iron ore (<50% Fe) will be 100% owned by Centrex without royalties. The Kimba Gap
project is located adjacent to Arrium’s existing hematite and magnetite mining operations."

If the Inferred Mineral Resource of 487Mt is "composed of magnetite bearing banded iron ore formation (“BIF”). Iron recovery for the total Inferred Mineral Resource shows that almost half of the iron within the BIF is weakly or non-magnetic (not magnetite). This is thought to be predominantly related to varying levels of oxidation of magnetite to hematite and goethite within the deposit." then surely Arrium have a decision to make re mining or collecting royalty??