I asked before via clienthelp, they will calculated based on when you invest them.
Basically each unit you buy has a date to it.
Say 4th October you invest and acquire 1000 unit, these 1000 unit will have a "expiry" date at 4th October 2017, after that u can redeem without charge.
Then you invest again on 9th December and obtain 2000 unit, these 2000 unit will have a "expiry" date at 9th December 2017, after that u can redeem without charge.
Same for subsequent investment which calculated based on investment date and distribution based on distribution date.
When u sell and redeem, FSM will auto calculate whether the amount you want to sell will incur ant charges or not.
They will follow first in first out principle
Using the above example, if you sell 1500 unit on 11th November 2017, your 1000 unit will not have redemption charge while the remaining 500 unit will have redemption charge
see the attachment below on how to sell the islamic bond, the system will tell u how many unit u can sell with redemption fee and how many without redemption fee.