Well found. After "that's" there are four evenly-spaced and distinctly-stressed syllables: "one, small, step, man", and "for" less prominent but equally distinct. No way there's anything else in there. No slurring, no swallowing. The syllabic peaks just don't allow for any "a", however unstressed.

Beyond that... long, long pause, and interference, and uncertainty. Maybe he realized he'd screwed it up, maybe he didn't notice. Very long hesitation: hard to say why. The latter parts have crackle. But there's no crackle in the first half.