What is the ruling on paying only 760 pounds or the full amount after adding another thousand pounds, given that the person from whom it was stolen does not believe the amount exceeded 1000 pounds?

If the bag was stolen without any negligence in its safekeeping, then he is not liable for it, as he is a trustee, and a trustee is not liable unless he transgresses or is negligent, based on the Prophet's (peace be upon him) saying: "A trustee is not liable."

However, if he was negligent in its safekeeping, then he is liable for what was damaged within it, because negligence with trusts necessitates liability. If his negligence is proven by evidence or by his own admission, then he must pay them what they claimed. But if they do not have evidence and he does not admit it, then his word, supported by his oath, is accepted, based on the Prophet's (peace be upon him) saying: "The burden of proof is on the claimant, and the oath is on the one who denies."

However, if he is not certain about what he claims, and his negligence is proven, and he wishes to clear his conscience, then he should pay them what they claimed.