NPC spell casting priority

[Shiny151]

Would someone be able to shed some light on how the NPC spell casting priority column works in the npc_spell_entries table?

For example, if I create an SK npc empowered with three procs/spells, does it make a difference if i set the priority of these three procs/spells 1,2 and 3 as opposed to 10, 20 and 30 in the priority column? (or any other varied numerical value for that matter)

Also, if I assign a parent list (perhaps the SK's baseline default spell lineup) in the npc_spells table in conjunction with these three additional procs/spells how are these additional procs/spells weighted against his parent spell lineup?