Someone admits Khalid has a right but leaves its nature unspecified. What is the next proper step?

Kitab al-Iqrar: Capacity, Unspecified Rights, and Amounts in Admissions

• Automatically treat the admission as 200 dirhams
• Ask the admitting party to specify the kind and amount of the right
• Always award the beneficiary 21 dirhams
• Treat every such admission as void