With supply protection, you can reserve minimum quantities for the demand of defined groups. Here you can define protection for stock transport orders or sales orders or combine both catalogs.
There is no option to define protection exclusively for contracts, but the fashion quantity contract is considered as well. The fashion quantity contract is treated like an ordinary sales order. If the contract matches a protection group, it is not restricted by this group and does also consume the protection.
However, there is a special logic regarding the call-offs: They are sales orders with reference to a contract. A call-off is not restricted by supply protection as long as the consumption of the contract can be transferred to the call-off. In other words, the consumption of the call-off takes place in the related time bucket of the matching protection group. At the same time, the consumption of the contract is reduced accordingly, and the protection is re-established.
Usually, the quantities of the call-offs can be confirmed, as there is no restriction and the quantities are already confirmed for the contract. There is no need that contract and call-off are matching with the same protection group. There is also no need that both protection groups have the same priority.
With this logic, supply protection can also be handled for contracts, so that call-offs will not be restricted by other supply protection objects as long as the call-offs do not exceed the volume of the contract.

step 1: The quantity contract matches a protection group

Step 2: The contract reduces the remaining protection

Step 3: The Call-Off replaces the Contract with the quantity of the Call-Off

Step 4: The consumption is shifted
Additional Information
Incident component for clarifications: CA-ATP-SUP
SAP Community Blog: Increasing Reliability with Supply Protection
SAP Help:
Manage Supply Protection