If the department considers mining in an Exploration Licence in Retention (ELR) area is viable, then you must either apply for a mineral lease or explain in writing why you haven't done so. If you don't apply, or the explanation is not accepted, the department can cancel the licence.
The area applied for under an ELR is calculated in hectares instead of blocks. It can be for all or part of your existing exploration licence area. If it covers the entire exploration licence area, the retention licence then replaces the original exploration licence. But if not, the EL remains in force for the remaining area.