• Hypothetical Coal Resource = the amount of coal in the investigation area or part of the investigation area, which is calculated based on data that meets the requirements set for the inspection investigation stage.
• inferred Coal Resource = the amount of coal in the investigation area or part of the investigation area, which is calculated based on data that meets the requirements set for the prospecting investigation stage.
• Indicated Coal Resource = the amount of coal in the investigation area or part of the investigation area, which is calculated based on data that meets the requirements set for the preliminary exploration stage.
• Measured Coal Resoured = the amount of coal in the investigation area or part of the investigation area, which is calculated based on data that meets the requirements set for the detailed exploration stage.

1. Low-Rank Coal calories: <5,100 kcal/kg
2. Mid Rank Coal calories: 5,100-6,100 kcal/kg
3. High-Rank Coal calories: 6,100-7,100 kcal/kg
4. Very High-Rank Coal calories: >7,100 kcal/kg

Source: Directorate General Of Minerals And Coal, Ministry Of Energy And Mineral Resources (Ditjen Minerba, KESDM)