Table:
| (In millions) | 2020 | 2021-2022 | 2023-2024 | Thereafter | Total |
| --- | --- | --- | --- | --- | --- |
| Long-term debt: (a) |  |  |  |  |  |
| Principal payments | $ 5,518 | $ 11,744 | $ 8,000 | $ 47,519 | $ 72,781 |
| Interest payments | 2,299 | 4,309 | 3,818 | 29,383 | 39,809 |
| Construction commitments (b) | 3,443 | 515 | 0 | 0 | 3,958 |
| Operating leases, including imputed interest (c) | 1,790 | 3,144 | 2,413 | 3,645 | 10,992 |
| Finance leases, including imputed interest (c) | 797 | 2,008 | 2,165 | 9,872 | 14,842 |
| Transition tax (d) | 1,180 | 2,900 | 4,168 | 8,155 | 16,403 |
| Purchase commitments (e) | 17,478 | 1,185 | 159 | 339 | 19,161 |
| Other long-term liabilities (f) | 0 | 72 | 29 | 324 | 425 |
| Total | $  32,505 | $  25,877 | $  20,752 | $  99,237 | $  178,371 |
Paragraphs:
Contractual Obligations
The following table summarizes the payments due by fiscal year for our outstanding contractual obligations as of June 30, 2019:
(a) Refer to Note 11 – Debt of the Notes to Financial Statements.
(b) Refer to Note 7 – Property and Equipment of the Notes to Financial Statements.
(c) Refer to Note 15 – Leases of the Notes to Financial Statements.
(d) Refer to Note 12 – Income Taxes of the Notes to Financial Statements.
(e) Amounts represent purchase commitments, including open purchase orders and take-or-pay contracts that are not presented as construction commitments above.
(f) We have excluded long-term tax contingencies, other tax liabilities, and deferred income taxes of $14.2 billion from the amounts presented as the timing of these obligations is uncertain. We have also excluded unearned revenue and non-cash items.
Question:
Why has $14.2 billion been excluded from other long-term liabilities?
Answer: We have excluded long-term tax contingencies, other tax liabilities, and deferred income taxes of $14.2 billion from the amounts presented as the timing of these obligations is uncertain.