What is difference on the aggregate intrinsic value between Outstanding and Vested and exercisable as of December 31, 2019?
{"Outstanding as of December 31, 2018": {"Number of Shares (thousands)": 4674, "Weighted-Average Exercise Price": 5.19, "Weighted-Average Remaining Contractual Term (years)": "", "Aggregate Intrinsic Value(1) (thousands)": ""}, "Granted": {"Number of Shares (thousands)": "\u2014", "Weighted-Average Exercise Price": "$ \u2014", "Weighted-Average Remaining Contractual Term (years)": "", "Aggregate Intrinsic Value(1) (thousands)": ""}, "Exercised": {"Number of Shares (thousands)": -842, "Weighted-Average Exercise Price": 2.84, "Weighted-Average Remaining Contractual Term (years)": "", "Aggregate Intrinsic Value(1) (thousands)": ""}, "Canceled": {"Number of Shares (thousands)": -130, "Weighted-Average Exercise Price": 9.41, "Weighted-Average Remaining Contractual Term (years)": "", "Aggregate Intrinsic Value(1) (thousands)": ""}, "Outstanding as of December 31, 2019": {"Number of Shares (thousands)": 3702.0, "Weighted-Average Exercise Price": 5.57, "Weighted-Average Remaining Contractual Term (years)": 3.52, "Aggregate Intrinsic Value(1) (thousands)": 6395.0}, "Vested and exercisable as of December 31, 2019": {"Number of Shares (thousands)": 3427.0, "Weighted-Average Exercise Price": 5.49, "Weighted-Average Remaining Contractual Term (years)": 3.56, "Aggregate Intrinsic Value(1) (thousands)": 6210.0}}
outstanding_agg_intrinsic_value = df["Outstanding as of December 31, 2019"]["Aggregate Intrinsic Value(1) (thousands)"]
vested_exercisable_agg_intrinsic_value = df["Vested and exercisable as of December 31, 2019"]["Aggregate Intrinsic Value(1) (thousands)"]
answer = outstanding_agg_intrinsic_value - vested_exercisable_agg_intrinsic_value