Lead Balloon
Mos 139 6.4 relates to holding points and in particular distance from centreline. This is where the 90m and 150 m graded strips largely come in. Precision approach runway holding points are even further back from centreline at a descending scale along the runway depending on elevation of the holding point in relation to the threshold.
Aircraft at a holding point, usually in line with the gables, are considered to be clear of the runway. But the holding point is often not coincident with the gables.
The 300m runway strip does not relate to ground markings or gables and I have never seen one marked, although it may happen. It is a distance off centreline for the surveyor to reference, not aircraft.