The 
indication falls on the 2nd beat of the bar in the sources. It seems highly unlikely that Chopin wanted to indicate exactly this place as the moment of reaching the forte dynamics, therefore, in the main text we propose to put the sign at the beginning of the bar. Chopin probably used here an earlier notation rule, according to which the signs were not placed at the beginning of the area covered by them, but somewhere in the middle. This type of notation can sometimes be encountered in his works. Cf. e.g. the notation of A in Etude in G
, Op. 10 No. 5, bar 83.
Compare the passage in the sources»
category imprint: Interpretations within context; Differences between sources
issues: Centrally placed marks
notation: Verbal indications