Here's is some suggested words that you could adapt to your circumstances/requirements.
Add new Z Clauses in Contract Data Part 1
[Clause #.# The Parties agree that the clarifications to Defined Cost stated in the Contract Data Part 1 are hereby applied to the [contract/agreement].]
Insert the additional text below in Contract Data Part 1 as appropriate
If Option A, C or E is used
Clarifications to Defined Cost
• The following items are included in Defined Cost: [insert clarification, you could you use the Schedule of Costs Components to clarify key cost heading as being included or exclude from Defined Cost]
• The following items/costs are expressly excluded from Defined Cost and including in the fee percentage: [insert clarification]