Looks like a bug to me.
I wonder if some of those stats are not actually pet stats, but are getting grouped with the pet stats? So maybe it's 8 magic acc for you, and 21 for your pet?
I'll test it with Nether Blast when I get home.
EDIT:
Nether Blast (naked): 1145
Nether Blast (wearing only Merlinic): 1507
Nether Blast (waring only NQ Apogee A): 1437
With 20/20 Magic Damage JP (+100), 19/20 BP Damage JP (+57), MAB +40 from Diabolos's BLM levels, MAB +23 from first 3 Gifts, MAB +10 from merits, MAB +20 from base Merlinic, MAB +21 from "first" augment, MAB +3 from "second" augment, and BP Damage +5% from base Merlinic that gives
(((99+2)*5)+100+57))*2.17*1.05 = 1508.367
If the "first" augment was for the master and not the pet, that would give us
(((99+2)*5)+100+57))*1.96*1.05 = 1362.396
If the "second" augment was for the master and not the pet, that would give us
(((99+2)*5)+100+57))*2.14*1.05 = 1487.514
So it would seem that both augments are for the pet. Please correct me if I made any mistakes or forgot to account for something.