The mark in the form of a diagonal cross written in FEH before the 1st grace note of the bar is probably a 
raising f
1 to f
1. At the same time, it cannot be excluded that, according to the intention of the writing person, it should apply both to this grace note and the first out of four small notes ending the trill. However, we have to point out that this mark may be simply one of the crosses with which Chopin would often mark the places discussed during a lesson.
category imprint: Graphic ambiguousness; Differences between sources; Corrections & alterations
issues: Annotations in teaching copies, Authentic post-publication changes and variants, Annotations in FEH
notation: Pitch