Gubong Mine Remaining ore reserves, page-2

0.15Mt is 150,000 Tonnes.
150000 X 6.4 (g/t) = 960,000 grams Au or 960Kg
At 32 (ish) Troy Ozs/Kg = 30,720 per year.

Or in other words, they lied about how much they mined.

Charles Barclay said as much in a London Conference earlier this year.
22000 workers at one stage. That's about 45 grams 1&1/2 Ozs per worker, per year. At 6.5 g/t, that's either pretty slack production or an outright lie.
A lot of people will believe official figures over believing an experienced mining engineer like CB. However, South Korea was a post war hell hole before General Park took over and modernised the country. No one in their right mind would have been honest about how much real gold and silver they were producing. It was a third world country and a battle to survive in those days.