Welcome to The Beach.
Although there is no official ratio, some of us use
www.fitday.com to check out our intake sometimes. You have to experiment and find what works for you but I sure as heck wouldn't worry about it the first few weeks!
As to serving size, reasonable is the key word. If you are not full, have a serving of a different allowable food. This is nutritionally the safest way to go. (Check out the FAQ for the revised list of Phase I allowables. )