NPC Spawn Issue: Raster of Guk

[girth]

Rasters PH is a 72 min spawn/despawn, but the rest of Lower Guk is on a 28 minute spawn, so the best way to maximize the amount of PH you get is as follows. (Times are obviously EQ times.)

5am - Spawn. Leave this one to despawn, unless it is Raster obviously.
8am - Despawn.
10am - Respawn. Kill this PH
7 to 8pm - Spawn. Also kill this PH

This method ensures 3 PH's per EQ day.

What does Bodi mean when he says the PH is a 72m spawn/despawn? I ask because he obviously doesn't take that long to respawn in his chart.