Put the meaning into your own words.

From the dates on the letters, she could deduce which journey occurred first.

Back at the newsroom, the journalist's analysis compared the message times, entrance log, and two witnesses' accounts. She marked one inference carefully: because the driver asked for entry, he probably did not have a working access code. That conclusion was reasonable but had not been stated directly by the driver. She could deduce something narrower from the confirmed timestamps: the access request preceded the organizer's reply, a sequence established by the records rather than by someone's guess.