Gram per meter stats provided by the manufacturer aren't always reliable.....and however far off they are would be multiplied by 60 or 70. I don't always take the diameters given as completely accurate either.
I have a pair of 8.4 mm ropes that weigh more than my old 9.0 mm's.
Same length.
I wanted to see how much I was saving for a long approach. I carried 8 ounces more.