There is a “science” to the numbers. Anything 7-10 causes great difficulty up to debilitating. 1 is no or almost no pain. But for those of us living every day with chronic pain, we tend to underplay the level because we “deal with it” every day. I can function with what most people would call 7-9. 10 means I can’t walk, usually because of back spasms. Other people would call what I consider 6-7 as a 9-10.