Proved reserves of coal – Generally

Proved reserves of coal – Generally taken to be those quantities that geological and engineering information indicates with reasonable certainty can be recovered in the future from
known deposits under existing economic and operating conditions.
Reserves-to-production (R/P) ratio – If the reserves remaining at the end of the year are divided by the production in that year, the result is the length of time that those remaining reserves
would last if production were to continue at that rate.