Try counting the number of measures for the different stanzas

( | 1 2 3 4 | 2 2 3 4 | 3 2 3 4 | . . . etc.)

What will be an ideal response?

If you count the first stanza very carefully from the first syllable of the word "Ko-ko- mo [me ba-by]" to exactly when the same syllable occurs again at the beginning of the second stanza, you will notice that the stanza seems to be 15-measures-plus-two-extra-beats long! This is because McDowell stretches out the usual twelve-bar blues stanza by adding a few measures. Then he actually adds two beats to the first measure of the second stanza on the word "Well." The second stanza thus starts out with a measure of six rather than the usual four beats per measure.
Adding a few extra beats—or even entire measures—to the usual twelve-bar stanzas was typical of the earlier rural (or downhome) blues that we hear exemplified in McDowell's "rural Mississippi juke-joint guitar style." Notice that the "stretching-out" of the blues stanzas does not in any way interfere with the hypnotic dance "groove" provided by McDowell's guitar playing.