I am now, have been and will be wrong

Math is fun.
Numbers aren't supposed to lie.
Except when they do.

Very simply: Do not use % to determine the amount of the market you'll capture.
It's naive, and short sighted to think you'll capture a small (3%) share of the market. If you do capture that amount, then you're either a bit player, or the market is too fragmented to be successful in. Either case, you're not attractive to an investor.

If you're making the argument that the market you're going after is HUGE, that's good. But why won't you be the one to make the majority market share? What's stopping you from getting 80% of the market? The thing that stops you from getting 80% of the market, is usually the SAME thing that stops you from getting 3% of the market.

The numbers are also misleading. Saying you'll get 3% of a Billion dollar market, meaning you'll get 30 million in sales, is just wrong. You won't get that amount, you won't compete, because the company that gets the first $970,000,000 will pick up the remaining $30,000,000.

If you can't give a good estimate as to the market size, and the amount you'll capture, how can you be credible on the execution of the business? Not knowing who's going to buy, how much they need your product, and what benefits they'll enjoy says a lot more about you and your team than it does about the market and the customers.