They had gold worth X to the market but X minus 11 billion on paper. So when France accounted for its gold in euro terms they would say they have X minus 11 billion Euros worth of gold.
Now they still have the same amount of gold but they "realized" a gain of 11 billion. They don't have that much cash left after the repurchase but now they say they have X Euros worth of gold which is 11 billion more than before.
So no they didn't make a profit from this as gold is higher on both sides of the Atlantic than last time they did their accounting updates.
> worth X to the market but X minus 11 billion on paper.
Why was it worth “X minus 11 billions”?
Probably based on the price they paid for it or when they last did some kind of asset accounting to calculate the Euro value of all assets held