Charles Still, b. 1760, was living in Uwchland, Chester County when that first census was taken in 1790.
The first number is the number of free White males aged 16 years and older. The government needed this figure to assess the country's industrial and military potential. The second number represents the number of white males under the age of 16 in the house. The third number is the number of white females, regardless of age. The fourth column is for all other free persons (this would be for example any free blacks). The final column is for any slaves.
In the above example, it looks like 1-3-5-0-0 for Charles Still. He naturally would be the older than 16 white male. I know he had three boys: Charles (b 1779), Henry (b 1780) and Jacob (b 1782). The third column indicates there are five (5) females in the house. One would be his wife Margaret Rhoades. One would be my 4th great grandmother Margaret (b 1788). I do not know the missing three females. The span between Jacob's birth in 1782 and Margaret's in 1788 certainly allows the possibility of additional children. Women then were indeed harder to trace since they normally did not leave home until they married.
The 1790 Census, according to the Census Bureau, was taken in the original 13 States, as well as the districts of Kentucky, Maine, and Vermont, and the Southwest Territory (Tennessee). Every 10 years since, a census has been taken. The information gathered differs from year to year.