It's not in that text you posted, which in when he was first asked, but it is not complete. In the full interview, he states that at the moment he decided to fire Comey, he was thinking about Russia. Go to 0:46 in this clip:
I don’t understand your point.
As for what Trump likely had in mind when he used the phrase "this Russia thing with Trump and Russia is a made-up story," later on he makes a remark, "I'm not talking about campaigns. I'm not talking about anything else. I'm not under investigation."
I don't know what is in your mind, what you are ascribing to Trump, with your "Trump says he was thinking about Russia," but I do know how I take Trump's remarks, viewing the interview in totality.