My wrist is about 180 mm. I measured for the Braided Loop using the (original) online tool, got 9 as a size, ordered a 9 and it was perfect.Lol I'm 180mm and couldn't even tolerate an 8, had to go with 9. I can't imagine how tight a 6 is. Hope it loosens up for you.
I am amazed that anyone with a 180 mm measurement would choose a size 6.
I'd be afraid it would interfere with my ch'i.