On the basis of the available photograph of As, it is impossible to interpret the L.H. part in the 1st half of b. 21. Chopin changed the text in the entire bar as well as at the end of b. 20; initially, that fragment most probably looked like that: 
(like most similar situations, it is only the 1st chord of each four that includes all noteheads). In b. 20 the top notes of the last two chords were then changed to a, whereas in b. 21 Chopin crossed out the e note in the 1st group and two last quavers in each group; in addition, at the beginning of the bar he added a new 1st half of the bar. On the photograph, the only thing to be seen there is a blot, yet its general outline seems to confirm the natural assumption that it is a very condensed, abridged notation of the final version, i.e. repeated c-g fifth. The text of this half of the bar is highly hypothetical, hence we put it in square brackets.
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category imprint: Corrections & alterations; Source & stylistic information
issues: Accompaniment changes
notation: Pitch