In the 2021-2022 Academic Year the term Suspension replaced Fixed Period exclusion.
When adding an exclusion period for a student, if the entry date is after 01/08/2021 you will only be able to select 'Suspension'.
If entering a historic exclusion period, if you enter a date earlier than 01/08/2021 you will only be able to select 'Fixed Period'.
Please see the Department for Education guidance here to verify this change (page 2).