Here's my rough understanding, from experience anyway: 50 is the level at which systems and processes start to become critical - you can't just succeed acciden

Here's my rough understanding, from experience anyway: 50 is the level at which systems and processes start to become critical - you can't just succeed accidentally through heroism, you have to deliberately set out to learn from and solve problems or you're sunk. 100 is the level at which people can no longer self-organize and need explicit constructs to manage organization. I.e. not just 'a pool of engineers who work on the product', but a X team and a Y team and a Z team. 150 is the level at which every person can no longer know everyone on a personal level at the company. You'll need some way to handle cooperation and communication that's not "Talk to Bob", and all hands meetings can only happen at best yearly. 500+ is the point at which things will generally become stabilized / ossified enough that the ongoing structure of the company either works or it doesn't and the difficulty of changing those things becomes exponentially higher. Reorganization is a significant misnomer.