#1 - you walk into a doctor’s office and ask what amount of insulin (brand A) should be injected by a Type 1 diabetic with a current\immediate blood sugar level reading of X (with the last reported injection Y hours ago), I bet you’d get an answer.
#2 - you walk in and ask how much insulin you should consume, you’ll get a blank look (at best) from the doctor.
Your OP is in the 2nd category.
I appreciate folk are at different levels of ability\experience and on a learning curve, and English is not everyone’s learning curve.
Whoever said you needed to “add XFF” - you should really ask them why followed by how. If they give you an answer on why but can’t give you an answer on how - I’d call bullshit.
Failing that - maybe explain what issue you are actually having.