What was the change in unearned license revenue between 2019 and 2020?
{"Unearned license revenue": {"January 31, 2020": 19, "February 1, 2019": 15}, "Unearned subscription and SaaS revenue": {"January 31, 2020": 1534, "February 1, 2019": 916}, "Unearned software maintenance revenue": {"January 31, 2020": 6700, "February 1, 2019": 5741}, "Unearned professional services revenue": {"January 31, 2020": 1015, "February 1, 2019": 767}, "Total unearned revenue": {"January 31, 2020": 9268, "February 1, 2019": 7439}}
unearned_license_2020 = df["Unearned license revenue"]["January 31, 2020"]
unearned_license_2019 = df["Unearned license revenue"]["February 1, 2019"]
answer = unearned_license_2020 - unearned_license_2019