in private pro app upgrade, what does 20 private users mean? is it about those roles etc?
It’s users of the app. The one big difference between Private Apps and Public Apps in terms of pricing is that Public Apps are charged per App, and Private Apps are charged per User.
I see, but what’s with the 20 though? does it mean the first 20 users will not be charged and after that 2 dollars each?
You pay for a minimum of 20 users per month.
The minimum charge is $40 per month*, and that gets you 20 users. If you have more than 20 users, then it’s another $2 per user. And it’s calculated based on active users, where an active user is one that signs into the app at least once during the month.
So for example, if you have 35 active users this month, then you’ll be billed $70. If you have 45 next month, then $90.
*If you pay annually instead of monthly, then you get a 25% discount
Have you read what it says on the Pricing Page? It seems pretty clear to me.