>" - I do not understand how 'mln' is more SEO than 'M'"
There are limits to how many characters and pixels Google and Bing will display before cutting off a title and appending an ellipsis. I believe that mln was chosen for stylistic reasons, to differentiate from molarity...
>"[Wikipedia] states that it's 'mol', but what do I know, I'm not a chemist"
'M' is used for molarity (molar concentration), not moles.[1]
There are limits to how many characters and pixels Google and Bing will display before cutting off a title and appending an ellipsis. I believe that mln was chosen for stylistic reasons, to differentiate from molarity...
>"[Wikipedia] states that it's 'mol', but what do I know, I'm not a chemist"
'M' is used for molarity (molar concentration), not moles.[1]
[1] https://en.wikipedia.org/wiki/Molar_concentration