Wow! I can't believe we've only ever mined 25 cubic feet of plat. Reading your source I'm not sure it's right, "The annual supply of platinum is only about 130 tons" "one cubic foot weighs a little more than 1,330 pounds"
23*1330lb = 13,875kg ever
130tons = 117,934kg per year
"basement of less than 25 cubic feet" Maybe them meant basement of 25 square feet or 250cuft which is still tiny basement.
So that's about 28.65 * 35.29 = 1011 cubic feet, JUST in South Africa and JUST between those years.
Other estimates visualise the total ever mined as a cube of 20 feet per SIDE ([2]), which sounds a bit more like it, given the numbers above - but still feels a little bit low.
23*1330lb = 13,875kg ever
130tons = 117,934kg per year
"basement of less than 25 cubic feet" Maybe them meant basement of 25 square feet or 250cuft which is still tiny basement.