How many times does Bill Withers sing "I know" in "Ain't No Sunshine"?

I know, I know, I know, you probably just spent a minute or two trying to count it out with your fingers. Withers had planned to write actual lyrics over the placeholder until Booker T. Jones, the band, and Graham Nash (who'd casually dropped in from his CSN session next door) talked him into keeping all 26. The tapping under each one isn't drums, it's Withers' foot on a box he brought into the studio.