Rowan,
Mine does the same.
Not sure about this as strictly TC does not exist after 23.59.59.24.
Since it is duration maybe 24+ is allowed.
If it loops back to zero it would be weird as it is equally weird that is goes to 24.
I do remember that in Shotlister this was specifically disallowed as it would generate a non standard EDL.
Gotta ask why you need this.