When you’re on the portfolio rebalancing page to review and approve the transactions, you see amounts that are based on the latest available NAV at the time.
Once you approve the rebalancing, all transactions are prescheduled (for different dates) by the system on the same day. This means that the reinvestment transactions are set (for a future date) as per the amount shown on the rebalancing page.
However, the redemption date may be different than the date on which you initiated rebalancing and therefore the NAV of the redemption date also can be slightly higher/lower than what it was on the date on which you initiated rebalancing. It’s because of this change in NAV that the redemption amount may also be slightly lower/higher than the reinvestment amount.