I was fired 8 years ago, in completing SF 86 question 13A.5 I have to provide a reason for leaving. Then the next portion has a time frame “in the last 7 years” have you been fired. I seems like I can’t answer the first part honestly without giving the details of the firing when the second part explicitly ask not to mention if under 7 years ago.
So, you answered your own question
In the section for answering reason for leaving, be honest. Just answer “terminated” No doubt the investigator will discuss it with you, to include what happened, who fired you, any prior write ups, etc. For the question that reads “in the last seven years” you can legitimately answer No if your termination was not within the 7 year window. If the Investigator asks about it, simply point out that it was over 7 years ago, and you had listed it under the relevant employment.
Both honest answers.