“I know your sitting down.” That is, where you stay.
“your going out and your coming in.” That is, what you do, how you live. This is the figure of speech polarmerismos, where two ends or extremes are put for the whole. An English example is, “That is the long and short of it,” meaning the essence of the whole matter. A person would go out of his tent or house in the morning and go back in at night, so to know their going out and coming in was to know their life.