The oil is lubricating the engine and very small quantities enter the cylinder. This is normal and not sth to be worried about. As Thinking said if there's no blue or white smoke coming from the exhaust then there's no issue.
It's normal for oil level to drop between 5-15% after 5,000-10,000 km. Best to keep it topped up. With extreme usage such as frequent hilly drives, speeding, operating in hot environment, etc. the oil level tends to drop more whereas in normal city conditions it will tend to drop less.