When Mark and Devon are applying the letters to the flood light, the close-up reveal shows the message spread out over three lines. In the wide shot where Devon leaves, the message is a single line.
Characters repeatedly speak of a "Miss Casey," but the captions instead read "Ms. Casey" (pronounced "Miz").
It makes no sense for Helly and Mark to assume that Lumon does not know about their exploration sortie through the corridors and to the Mammalian station. They saw the monitors in the control station and should have realized that Lumon is all about constant secret surveillance.
It makes no sense for Reghabi to insist on talking to Mark inside his car. She should know better than anybody else that Lumon is all about constant secret surveillance and there is a high probability that they bugged Mark's car.