Put the meaning into your own words.

The dated photograph supplied conclusive evidence that the tower already existed.

A campus journalist was investigating why a delivery missed the student book fair. Her firsthand account came from watching the driver wait at a locked entrance, rather than hearing the story from another reporter. A time-stamped message could corroborate her observation that the driver had requested access. Neither item was conclusive about who had locked the door, however, so she separated what the material supported from the larger question that still required an answer.