FTP rakeback + deposit bonus, negative rakeback

[foal]

So I have rakeback with rakereduction.com. I notice after playing my first 389 hands that I have 4.00 toward my 600 bonus and -3.5 in rakeback. I understand that the two don't work well together, just a few questions if anyone can give me more info:

How badly is the bonus going to hurt my rakeback account? Will I be like -500 in rakeback by the time I clear it? Do I actually owe them money when it's negative?

Oy.