Those two midpoints are located at more or less the same place. a midpoint is repeated every 45 degrees, so each midpoint is found 8 times in the circle. i'd give a midpoint a 1.5 degree orb, and midpoints with angles or the sun/moon a 2 degree orb.
When a planet transits around 6 degrees of any mutable sign, or 9 degrees of any fixed sign (45 degrees from 6 degrees of a mutable sign, it will stimulate both midpoints.
If a planet sits at 6 degrees of any mutable sign, or 9 degrees of any fixed sign, that then planet can be further interpreted (after sign, house and aspect) in terms of the nature of the midpoints. ie: someone with sun at 6 pisces experiences their pisces sun in a way that involves frustation, loss, guilt (saturn/neptune) as well as a broadening of the mind (mercury/jupiter).