"To qualify for any payouts, the Referred Host’s first received booking must have a value (excluding cleaning fees, taxes, and special offers) of at least 100 USD (or the equivalent in your local currency)."
Looks like you found the answer, @Paul-and-Susan1.
If you would like to see a change in the terms and conditions of the program, you might mention it in Host Voice. That is in the dropdown under "Discuss" at the top of this forum. Look first to see whether anyone else has posted on it. If they have, give it a thumbs up. That is how suggestions get attention.
Just by the way, this is why I always turn down the offer of referring my friends. None of them has a $100 place 🙂