What was the change in the Total compensation of key management personnel  in 2019 from 2018?
{"": {"Year-ended 31 March 2019": "$M", "Year-ended 31 March 2018": "$M"}, "Short-term employee benefits": {"Year-ended 31 March 2019": 6.6, "Year-ended 31 March 2018": 9.1}, "Post-employment benefits": {"Year-ended 31 March 2019": 0.1, "Year-ended 31 March 2018": 0.1}, "Share-based payments - equity-settled": {"Year-ended 31 March 2019": 10.4, "Year-ended 31 March 2018": 17.7}, "Total": {"Year-ended 31 March 2019": 17.1, "Year-ended 31 March 2018": 26.9}}
total_2019 = df["Total"]["Year-ended 31 March 2019"]
total_2018 = df["Total"]["Year-ended 31 March 2018"]
answer = total_2019 - total_2018