We understand this from the word "sprout," which refers to God allowing the earth to produce plants through germination (sprouting).
There are a number of other assumptions implicit in the calculation.
In fact, the original biblical languages contained many fewer words than modern English, which means that the words in those languages had more different meanings.
In the Genesis 1 creation account, each "day" ends as "evening and morning 'n' day," where "n" is the day's number.
We don't know how long Adam worked the garden before God gave him another assignment.
However, it wouldn't have been much "work" if Adam was there for less than 24 hours.
By cross referencing the biblical genealogies with other events dated in the Bible, one can find instances where numerous genealogies were telescoped, resulting in the exclusion of numerous generations of individuals.