In general, an expansion is more tricky. In an expansion, we sell FLOAT to the market for 100% of its Target Price + some additional amount. When the Basket Factor is below 100%, every additional FLOAT sold (and therefore ETH is received in return) is effectively increasing the Basket Factor closer to 100%. In contract, when the Basket Factor is above 100%, every additional FLOAT sold effectively decreases the Basket Factor closer to 100%. In any expansion, BANK holders get rewarded with the profit from the trade. In a contraction, if the Basket factor is below 100% they are taxed due to the increase of supply.