What is the distinction between testifying about a simple statement of debt and testifying about an explicit declaration of obligation?

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There are two distinctions between hearing someone simply state 'So-and-so owes so-and-so a thousand dirhams' (which permits testimony) and hearing a witness say, 'I testify that so-and-so owes so-and-so a thousand dirhams' (which does not permit testimony without a specific request). First, the declaration of testimony carries the connotation of knowledge, whereas a simple statement of debt can carry the connotation of an acknowledgement (Iqrar). Second, acknowledgement is broader in its binding effect than testimony; it is valid for unknown amounts and does not require specific numbers or qualifications, unlike testimony. Acknowledgement is a statement made by a person concerning themselves and is less suspect, thus stronger than testimony.