You can make up numbers forever but a realistic method is to work out "playing forward" from release for 2 years ... How many will you get in the first month and how will you get them?,
Then the next 3 months how many, how do you get them, how much do they cost on average to get, how much do you bring in from them?
How many dev, support, sales people?
How much in advertising?
Repeat forward quarter by quarter for 2 years ... Where are you at? Have a good and a bad version, take the aveage and you should be close.
If you actually do better that's great but this is realistic numbers investors can believe.
For extra credit do a with and without funding version.
Will pwople read it? Probably not, the main thing this will help with is your ability to talk intelligently to investors because you will have thought about it first.