Tax does not include withholding tax in the Tax Estimate because withholding tax forms part of PAYG withholding, not income tax. Calculating it would require assumptions about your country of residence when the income was paid or accrued, whether the payer actually withheld and sent the tax to the ATO, and whether you were a resident for only part of the year.
Your notice of assessment shows the tax you owe on your taxable income, includes any offsets you are entitled to and shows credits for tax already paid. Under section 128D of the Income Tax Assessment Act 1936, income that has been subject to withholding tax is not included in assessable income, so it is excluded from assessment.
Australian residents who pay interest, dividends or royalties to foreign residents must generally withhold tax and pass it directly to the ATO. The person controlling the payment must withhold enough to cover the tax owed.
For more details refer to the relevant ATO guidance.