It’s an old principle of copywriting that putting a number in the headline is a good way to attract readers’ attention prior to trying to sell them whatever you're selling. It suggests there’s going to be substance and specifics in what follows.
It can be positive ("3 Ways To Turn Your Catbox Waste Into Dollars") but negative works, too ("6 Things You Should Never Do While Riding A Bicycle").
People on LinkedIn have taken the technique `a outrance. You’ll find dozens if not hundreds of posts in that pattern, some less reasonable than my examples above.
Since the delivery is by its nature authoritative, presumably each is written by an authority on that subject.
Is that likely? If all those people know all those secrets and are kind enough share them with everyone else, there should hardly be any problems left in the world. We’d all know how to manipulate employees, cozzen our bosses, write perfect “content,” and Avoid These Five Mistakes When Quitting our Job. Everyone would be making money in a corner office / at home / in their pajamas / sitting at the beach, by writing / teaching (anything) / telephoning / composting... Surprising that we still have high unemployment and poverty.
That’s not to say there aren’t gems scattered around in the mulch, but it takes a lot of reading, or at least sampling, to sift them out. Most of the time I ignore them, but some will intrigue me with what seems like a particularly pertinent line and I’ll go for it.
Most of those times I find lists of things I already know, particularly if the subject is writing. I think any seasoned writer would have the same reaction. There are just so many principles, tips, and tricks you can read before you realize you've seen it all before. Maybe you learned it under a different title; a lot of old ideas have been recycled for the new market.
And one of them is the numbers game, so I’m thinking about getting into it myself. First post will be "10 Reasons You Shouldn’t Believe Everything You Read on LinkedIn," subhead "5 will get you 8 probably 90 percent of it is old news."