A more thorough explanation:

Definition: Ut res magis valeat quam pereat is a Latin phrase that means "to give effect to the matter rather than having it fail." It is a maxim of construction applied when alternative readings are possible, one of which (usually the broader reading) would achieve the manifest purpose of the document and one of which (usually the narrower reading) would reduce it to futility or absurdity, whereby the interpreter chooses the one that gives effect to the document's purpose.

Example: A company's employee handbook states that "employees are entitled to a 30-minute lunch break." An employee argues that this means they are entitled to exactly 30 minutes for lunch and cannot take longer. However, the company argues that the purpose of the policy is to ensure that employees have adequate time to eat and rest during their workday. Therefore, the broader reading of the policy would be that employees are entitled to at least 30 minutes for lunch, but they can take longer if needed to fulfill the purpose of the policy.

This example illustrates how the maxim of ut res magis valeat quam pereat is used to interpret ambiguous language in a way that gives effect to the purpose of the document. In this case, the purpose of the employee handbook is to ensure that employees have adequate time to eat and rest, so the broader reading of the policy is chosen to achieve that purpose.