Autocomplete rule to default Offer DFFs from Valueset

Summary:

While creating Job Offers, there are certain DFFs where I want to default field values based on a query-based value set. Currently, the dropdown shows only the expected value — which varies for each candidate offer, as it's fetched dynamically from another source via the value set's query.

Even though only one value appears in the dropdown, we want this value to be automatically defaulted into the DFF field and set as read-only. I understand this might be achievable using autocomplete rules.

Can anyone please guide on how to configure the function or condition when using the Defaulting Value Rule