In month n, you have U_0 x (1 + monthly growth)^n users.
Does that look familiar? Be honest.
That’s modeling hockey-stick growth by defining exponential, hockey-stick growth. Then the game is tweaking the growth rate to make the numbers look reasonable. You lower the growth rate so your projections aren’t totally insane — just insane enough to make you a millionaire on paper.
This kind of model is an exercise in vanity, because it makes you feel like a billion-dollar valuation is just one tiny tweak away to that growth-rate cell on your spreadsheet.