First, you need to know that (at least in SI) "m" is for "mili" - a thousandth part of something, and "M" is for "mega", which means "a million units".
So, 100m is 0.1 headlines.
One thing is if I could understand it and another thing is if the author's writing skills are good enough to advise others about writing.
BTW, the submitter (or a moderator) seems to agree with me (check the current HN-entry title).