What is the ruling on an acknowledgment of debt by an heir when there are multiple heirs?

Primary text

If the debt were established by evidence, the statement of the deceased, or the acknowledgment of all heirs, the heir would only be liable for half. His individual acknowledgment should not obligate him for more, similar to a bequest. Furthermore, his testimony regarding the debt alongside others is accepted, but if he were obligated for more than his share, his testimony would not be accepted because it would draw a benefit to himself.