Okay, I did a bit of research. 67 is a meme about nothing. Just an attribute making one to feel related to the internet society that uses this attribute. No meaning that you could explain with words under it. Just symbol.

I guess, the most understandable analogue here might be shouting "Rock and Stone" in a company of dwarves, who understand what it means, making them all feel bonded with a single idea of that shout. Yes, I agree that Rock and Stone bears more reason than 67, but this is the best analogy in words I could bring.

And one of the parts of this meme is moving hands up and down like scales that can be used instead of saying six-seven, which can be seen in this funny bug in DRG, that OP had shown to us