As Betty and Barnaby are wondering what "C.G." means on Gordon's desk calendar, Barnaby asks Betty to look for a similar notation on an earlier date. Betty turns pages backwards five times to June 19th. It was established that Gordon's "C.G." lunch was on a Friday, but June 19th in 1973 was on a Tuesday, only three days earlier, not five.
The pilot is instructed to take off on runway 35 left. There was only a single runway in that direction so the designation left would not be used. Left and right designations are used when there are parallel runways.
The pilot takes off from runway 35, which 350 degrees or ten degrees left of due north. The plane is traveling almost due north, but the sunlight is shining almost directly onto the front of the plane which means the sun would have to be due north in the sky, an impossibility in North America.
The gunman trying to shoot Barnaby has a silencer on his gun, but the full report from the gun with no muffling can be heard. In fact, it is as loud as Barnaby's gun which had no silencer.
A gunman in the parking garage uses a silencer on a revolver. That would not do anything to reduce the sound of the report. Silencers only work on semi-automatic pistols. That's why Barnaby's shots are as loud as the gunman's.