You can whitelist subIds on offer level by using the advanced targeting feature.
In order to do that:
Go to the offer details page
Click on the Targeting tab
Select Publisher > Sub ID with operation in (as per the image below)
Insert in Value the subid that you would like to whitelist
Tip
Keep in mind that this will apply to every publisher that is approved on the offer, meaning that if any publisher is sending clicks from a subid that is not on the list, that click will be discarded.
You can find those Discarded Clicks under the reason ADVANCED_TARGETING_MISMATCH