For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
I personnaly believe Adam and Eve were in the garden for many years. I base this presumption on the fact that GOD told Adam and Eve to be fruitfull and multiply, so while they lived within the garden, they were of age to conceive and bear children after their creation. As to the number of children Eve birthed that is unknown, but the children after they reached deep into puberty, most likely left the garden, because of the law gave to Adam and Eve then passed on to their men and women. Genisis 2:24 Therefore a man shall leave his father and mother and be joined to his wife, and they shall become one flesh. And since incest was not taboo yet, the marriage of brother and sister was legal.