[mhluongo]

When something is "realized" is a matter of accounting. It means to make the change, they sold the gold fo currrency, then bought it back. For many of us, realizing a gain is when taxes happen, though I'm not sure what it means for a nation state.

https://www.investopedia.com/terms/r/realizedprofit.asp

[mort96]

So they could sell it again and buy it again and realise another $15b?

[atombender]

No, there wouldn't be any gains to realize — unless the gold price went up since they bought it, of course.

If you buy something for $10 and sell at $15, you realized a gain of $5. If you then buy at $15 and sell it at $15, you realized a gain of $0.