According to the Security Classification Guide, if a new document states "The task will take three hours to complete," how should this information be marked?

The correct classification for the statement "The task will take three hours to complete" is unclassified. This is because the information does not meet the criteria for any level of classified information. The classification of information is guided by whether its unauthorized disclosure could cause damage to national security. In this case, the statement is simply a logistical detail regarding the time required for a task, which does not have sensitive implications.

Classifications such as Confidential, Restricted, and Secret are reserved for information that could harm national security if disclosed, but the specified statement does not contain any sensitive or classified information that warrants such a classification. Therefore, marking it as unclassified is appropriate and aligns with the guidance provided in the Security Classification Guide.