It's The Lesson, Not The Money
It's not about how much Ruth is giving to her parents as rent, but the symbolism behind it.
QUESTION: Ruth is 19 years old and lives with her parents. They just started the Baby Steps and she has a part-time job that makes $400 a month. How should she help out with expenses? Should it be a percentage or fixed amount?
ANSWER: You’re not making enough to contribute much, so you guys negotiate that out. It’s more a symbolism of your character and your willingness to contribute rather than what you are contributing. If you give them the $400 a month, it doesn’t change their lives. Giving $100 would be very fair, but it’s whatever you can sit down and work out. But you paying rent won’t change their situation. The only thing we’re trying to accomplish is a lesson here for you.