How are Prices reviewed for a compensation event that is an instruction from the Employer?
The Project Manager would instruct the Contractor to submit a quotation. The Contractor would submit a quote and the Project Manager would either accept the quote or not, and if not either ask them for another quotation or can assess it themselves if they do not believe it has been assessed correctly. It will depend on which primary option the Contractor is working under as to which schedule of cost components they use to assess the quote and what the change to the Prices will be.
I suggest you have a read of section 6 of the contract and after that it should make fairly good sense.