What is the difference in notional amount between those less than 1 year and 1-3 years?
{"Foreign exchange forward contracts -- 2019": {"< 1 year": 1.0, "13 years": 1.0, "Total": "Total"}, "Foreign exchange forward contracts -- Notional Amount (USD millions)": {"< 1 year": 517.0, "13 years": 176.0, "Total": 693.0}, "Foreign exchange forward contracts -- Average forward rate (SEK/USD)": {"< 1 year": 9.13, "13 years": 8.92, "Total": "\u2013"}}
less_than_1_year = df["Foreign exchange forward contracts -- Notional Amount (USD millions)"]["< 1 year"]
between_1_3_years = df["Foreign exchange forward contracts -- Notional Amount (USD millions)"]["13 years"]
answer = less_than_1_year - between_1_3_years