While rebalancing, the sell are carried out first. The sale proceeds are then used to carry out the buy orders. 

As the buy orders are placed on the next trading day, there is a possibility that the prices of those stocks recommended for buying may change. Hence, your approval is taken on value instead of quantity. Once approved, the orders will be placed based on the recommended value. The quantities are updated based on the current market prices of recommended stocks at the time of placement.