What is the ruling when Khul' is done for an unknown quantity of something whose difference in value is not great, such as a slave (عبد)?

Primary text

When the exchange for *Khul'* is an unspecified but existing item like 'a slave' (عبد مطلق) or multiple slaves, the contract is valid. If he stipulates 'a slave,' the divorce becomes effective immediately upon her providing any slave, and he receives ownership of that slave only. If he stipulated 'slaves' (plural), he receives three slaves. This is the apparent position of Ahmad and the implication of the ruling of Al-Kharqi. The evidence is that the condition for divorce is met upon giving him the named item, and she is not obligated to give more because she did not commit to a specific amount beyond the name.