I've been reading up on the chord numbering system and think I understand most of it. On a chord chart, designations of major chords are shown by a chord number, and altered chords (such as minor, 7th or sus4) would normally be shown as the chord number followed by a suffix (such as m, 7 or sus4). Other variations may show the minor as a minus sign, or a lower-case Roman numeral.
Regardless, two questions I haven't found the answers to yet:
1. How do you show a chord that is not part of the range (I-II-III . . .)?
Example: Playing a song (say in the key of C) and part of the chord progression goes: F Fm C D7 Ab G C
The chord chart could say: IV iv I II7 [X] V I
How would you designate the spot for the Ab (the [X] above)? Would you show it as bVI? How about #V?
2. How do you designate key changes that occur in the middle of the song?