Because the successful redemption cannot be confirmed until the end of trading hours on Friday.
If the redemption is from a currency fund, it must be deposited into the account next Tuesday.
If you redeem a stock or hybrid fund, it will not arrive in your account until the next Friday.
That means it takes 7 days to get to your account.
No matter when it arrives in the account, it will be calculated based on the net value of the fund on the day when the redemption is confirmed.