MIDI-CI messages are transmitted as Universal System Exclusive messages. (In the
MIDI-CI spec, see printed page 16 / PDF page 21 "Standard Format for MIDI-CI Messages".) All the data bytes in a System Exclusive message have the most significant bit clear.
As explained in a previous thread (
Question after reading the MIDI-CI 1.1 Spec RE: MUIDs), FFFFFFF and 7F 7F 7F 7F are two different representations of the same 28-bit value (28 one bits):
FFFFFFF represents the value in the continuous range from 0 to FFFFFFF.
7F 7F 7F 7F is how the value is encoded into four System Exclusive data bytes.