Powerful Build (half-giant), large weapons and Wield One Step Greater No Penalty?

(v6.04.00)

Powerful Build (Ex) Can be treated as one size larger if advantageous for size modifier for opposed checks, special attacks affected by size, and using weapons. This stacks with other size-changing effects.

Trying to understand effects of the custom equipment modifier Wield One Step Greater No Penalty with large weapons, in relation to this ability.

Specifically, why does the modifier [MAGIC] shifts from +1 to +3 (see below)?

From the troubleshooting.htm:

Attacks Masterwork Shortspear (Large/Wield One Step Greater No Penalty) Melee; Number of Attacks: 1; Crit: 20; Crit Multiplier: x2; Reach: 5 ft. To Hit: +11 = +5[BAB] +2[STAT] +0[SIZE] +3[MAGIC] +1[MISC]

Damage: 1d8+3

Masterwork Shortspear (Large/Wield One Step Greater No Penalty/Thrown) Ranged; Number of Attacks: 1; Crit: 20; Crit Multiplier: x2; Range Increment: 20 ft. To Hit: +10 = +5[BAB] +3[STAT] +0[SIZE] +1[MAGIC] +1[MISC]

Damage: 1d8+4;

Masterwork Shortspear Melee; Number of Attacks: 1; Crit: 20; Crit Multiplier: x2; Reach: 5 ft. To Hit: +9 = +5[BAB] +2[STAT] +0[SIZE] +1[MAGIC] +1[MISC]

Damage: 1d6+3

Masterwork Shortspear (Thrown) Ranged; Number of Attacks: 1; Crit: 20; Crit Multiplier: x2; Range Increment: 20 ft. To Hit: +10 = +5[BAB] +3[STAT] +0[SIZE] +1[MAGIC] +1[MISC]

Damage: 1d6+4;

I tried attaching the pcg file and got this message: The extension pcg is not allowed. Same thing with text...