You tell me what am I missing. They had $17,645,500,000 in unlevered FCF last quarter. With $32,695,000,000 in Cash and CE on their balance sheet.

Edit: I see the gap now with your question. The buyback plan/funds are not executed all at once. A company approves amounts to be used for buybacks and then it happens over time. My point is that these buybacks are pretty normal for apple. You can look at Apples historical buyback plans and I think the last announced one was a year ago for $90b.