FAR 17.207  (f) Before exercising an option, the contracting officer shall make a written determination for the contract file that exercise is in accordance with the terms of the option, the requirements of this section, and part  6. To satisfy requirements of part  6 regarding full and open competition, the option must have been evaluated as part of the initial competition and be exercisable at an amount specified in or reasonably determinable from the terms of the basic contract, e.g.-

           (1) A specific dollar amount;

           (2) An amount to be determined by applying provisions (or a formula) provided in the basic contract, but not including renegotiation of the price for work in a fixed-price type contract;

           (3) In the case of a cost-type contract, if-

                (i) The option contains a fixed or maximum fee; or

                (ii) The fixed or maximum fee amount is determinable by applying a formula contained in the basic contract (but see 16.102(c));

           (4) A specific price that is subject to an economic price adjustment provision; or

           (5) A specific price that is subject to change as the result of changes to prevailing labor rates provided by the Secretary of Labor.

So you can see from this the option is to be exercised as written in the contract.

From the information provided we have no way of knowing the specifics of all of the contracts that need an extension.  We don’t know if in the basic contract you had set total hours or total number of people.  In general the option to extend should match with what is in the basic contract.