'f' is the note with the episema change 'f' for a note 4 tones higher 'j' in this case. The episema should now be above the note. Of course, if you re-compile the .gabc you'll have to repeat this.
A user asked on the gregorio-users mailing list on 8/12/2011 whether there is a way, using gabc, to position the ictus/vertical episema above a note rather than below it. His question wasn't answered, alas.
It sounds like this would be a good proposal for a feature enhancement!
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