1.5 is an unofficial phase used by many here. It's what we call the transition from Phase 1 to Phase 2 when you slowly and carefully add fruit and grains back into your diet. Some of us have found that Phase 1.5 is were we end up either because we are extra sensitive to grains or to fruit. So 1.5 can be anything on the Phase 2 list.
1.5 is a great time for you to start learning what works for your body. What foods in combination with other foods work best? Is time of day an issue for you (some people can;t have grains in the morning, some at night, others have no such issues).
One of the best things about South Beach is really learning the unique factors that work best for your body.
Here are some links to earlier discussions:
Phase 1.5/2 questions
Who is still on phase 1.5
Emergency Handbook for Phase 2
What's Your P2 Combo?
Baby steps, getting back on track 2015
48 lbs maintained since 6/08