The Norway defender joined the Bees ahead of their maiden Premier League campaign.
"They said they had seen 123 matches with Celtic and they provided feedback on which matches were green and approved and which were red and not acceptable," Ajer told TV2.
"They analyse everything, so what I liked about the club compared to the others was that they said there were a lot of exciting things about me that they were interested in, but also that I had to improve."
Ajer also revealed the attention to detail of Bees assistant manager Brian Riemer.
He continued: "He often sends me messages during the week and writes: 'Have you seen this situation? What happened? What are you going to do differently?'. And then it's just about getting in and finding out what situations he's talking about. He thinks football 24/7."
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