What was the change in the recurring revenue from 2018 to 2019?
{"Revenue: -- Recurring revenue": {"2019": 1395869.0, "2018": 1411742.0, "2017": 1176720.0, "2019 % Change from 2018": -1.1, "2018 % Change from 2017": 20.0}, "Revenue: -- Non-recurring revenue": {"2019": 375808.0, "2018": 338220.0, "2017": 320988.0, "2019 % Change from 2018": 11.1, "2018 % Change from 2017": 5.4}, "Revenue: -- Total revenue": {"2019": 1771677.0, "2018": 1749962.0, "2017": 1497708.0, "2019 % Change from 2018": 1.2, "2018 % Change from 2017": 16.8}}
recurring_revenue_2019 = df["Revenue: -- Recurring revenue"]["2019"]
recurring_revenue_2018 = df["Revenue: -- Recurring revenue"]["2018"]
answer = recurring_revenue_2019 - recurring_revenue_2018