How much is the difference between Unguaranteed and Guaranteed residual value of Investment in Sales-Type and Direct Financing Leases?
{"($ in millions) -- At December 31, 2018:": {"Investment in Sales-Type and Direct Financing Leases": "Investment in Sales-Type and Direct Financing Leases", "Commercial Financing Receivables": "Commercial Financing Receivables", "Client Loan and Installment Payment Receivables/ (Loans)": "Client Loan and Installment Payment Receivables/ (Loans)", "Total": "Total"}, "($ in millions) -- Financing receivables, gross": {"Investment in Sales-Type and Direct Financing Leases": 6846, "Commercial Financing Receivables": 11889, "Client Loan and Installment Payment Receivables/ (Loans)": 13614, "Total": 32348}, "($ in millions) -- Unearned income": {"Investment in Sales-Type and Direct Financing Leases": -526, "Commercial Financing Receivables": -37, "Client Loan and Installment Payment Receivables/ (Loans)": -632, "Total": -1195}, "($ in millions) -- Recorded investment": {"Investment in Sales-Type and Direct Financing Leases": 6320, "Commercial Financing Receivables": 11852, "Client Loan and Installment Payment Receivables/ (Loans)": 12981, "Total": 31153}, "($ in millions) -- Allowance for credit losses": {"Investment in Sales-Type and Direct Financing Leases": -99, "Commercial Financing Receivables": -13, "Client Loan and Installment Payment Receivables/ (Loans)": -179, "Total": -292}, "($ in millions) -- Unguaranteed residual value": {"Investment in Sales-Type and Direct Financing Leases": 589, "Commercial Financing Receivables": "\u2014", "Client Loan and Installment Payment Receivables/ (Loans)": "\u2014", "Total": 589}, "($ in millions) -- Guaranteed residual value": {"Investment in Sales-Type and Direct Financing Leases": 85, "Commercial Financing Receivables": "\u2014", "Client Loan and Installment Payment Receivables/ (Loans)": "\u2014", "Total": 85}, "($ in millions) -- Total financing receivables, net": {"Investment in Sales-Type and Direct Financing Leases": 6895, "Commercial Financing Receivables": 11838, "Client Loan and Installment Payment Receivables/ (Loans)": 12802, "Total": 31536}, "($ in millions) -- Current portion": {"Investment in Sales-Type and Direct Financing Leases": 2834, "Commercial Financing Receivables": 11838, "Client Loan and Installment Payment Receivables/ (Loans)": 7716, "Total": 22388}, "($ in millions) -- Noncurrent portion": {"Investment in Sales-Type and Direct Financing Leases": 4061, "Commercial Financing Receivables": "$    \u2014", "Client Loan and Installment Payment Receivables/ (Loans)": 5086, "Total": 9148}}
unguaranteed_residual_value = df["($ in millions) -- Unguaranteed residual value"]["Investment in Sales-Type and Direct Financing Leases"]
guaranteed_residual_value = df["($ in millions) -- Guaranteed residual value"]["Investment in Sales-Type and Direct Financing Leases"]
answer = unguaranteed_residual_value - guaranteed_residual_value