Positive economics is analysis that generates objective descriptions or predictions about the world that can be verified with data. It is analysis that describes what people actually do. "A 5% fall in the unemployment rate will lead to a 2% increase in the inflation rate" is an example of a positive economic statement.
On the other hand, macroeconomics is the study of the economy as a whole. The scope of macroeconomics extends to the study of economy-wide phenomena, like the growth rate of an economy, the nation-wide unemployment rate, or the inflation rate. Robert and Janet are discussing unemployment and inflation in their country.