What is the legal implication of stating a debt of a thousand, with the exception of 'a thing' (illa shay'an)?

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When a person states, 'He owes me a thousand, except a thing,' the exception (al-shay') must be interpreted as less than five hundred dirhams (half of the total debt) before its meaning is determined. This is because 'a thing' is ambiguous, encompassing both small and large amounts, but excluding more than half is necessary. Therefore, it must be taken to mean less than half.