Up/ Down Arrows with Figure Parameter: How far is a click?

Do you want to do edits on a phrase, or do you want to use chord inversions in a chordprogression ?

The only thing that can be said with certainty is that the arrow keys move the selected phrase segment one line up or down in the phrase editor grid. What this means musically depends on many factors, among others: The symbol type (color) of the phrase, the settings at the interpretetation parameter, the harmonic context, the setting 'bypass voice leading' on or off, the phrases at the other instruments, the settings for the pitch ranges and typical pitches, and so on. Honestly, I have given up long ago to try to understand exactly what and why Synfire does or does not in a particular situation. Meanwhile, I am perfectly satisfied that I get good musical results. I do not necessarily understand everything.

So, perhaps the best answer to your question is: If you select a phrase segment and press the arrow up key then it will tend to sound a bit higher (probably one scale step) and if you press the arrow down key it will probably sound a bit lower. 

I often treat synfire as a magic box, only my ears tell me if its good or bad magic that it weaves with each change, and my mood dictates if the change, good or evil, stays or gets cmd-zeded... Lol
But Juergen is right, generally the up arrow makes the pitch higher and the down, lower. That is unless playing ranges or something else dictate an inversion is needed.