The math is simple. One Bitcoin had a value of 0,008 $ and this is 1/125 of a dollar. one dollar then will give you 125 Bitcoins, in this case 1000 times. This is 12,5k BTC worth about 250 billion compared to todays value. In 2010 there was probably not mined such amount of Bitcoin, so the example is just hypothetical.
If Citybank prediction go in and you invest $1000 today you'll have Bitcoin worth $15k in the end of 2021. Not bad, right?