The top o is the root (or tonal center) of the mode, and | equals a whole step.
ionian
(major)
Maj7
dorian
--
m7
phrygian
--
m7
lydian
--
Maj7
mixolydian
--
7
aeolian
(minor)
m7
locrian
--
m7b5
The top o is the root (or tonal center) of the mode, and | equals a whole step.