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

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mort96 2 hours ago | parent [-]

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

	▲	atombender an hour ago \| parent [-]
		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.