Mist vs. Shadow Options

[phlapjack77]

Mist (Environmental, Area)
Type: P • Range: LOS (A) • Duration: I • DV: (F ÷ 2) + 3
Mist creates a thick fog that fills the entire area of effect.
The mist is dense and difficult to see through, imposing a visibility
modifier equal to the hits scored by the caster. Because
the spell is not sustained, the mist dissipates quickly, based
on the surrounding temperature and winds; reduce the vision
modifier by 1 per Combat Turn.


Shadow (Environmental, Area)
Type: P • Range: LOS (A) • Duration: S • DV: (F ÷ 2) + 1
Shadow creates a globe of darkness with a radius equal to the spell’s
Force in meters. Every hit imposes a –1 die pool visibility modifier
against targets within the area (maximum –6).


The only difference that I can see between these two spells is that Mist is Instant, whilest Shadow is Sustained. In the spell creation rules of Street Magic, Duration of Instant and Sustained are both +0 DV.

So why does Mist have a DV of (F/2)+3 and Shadow a DV of (F/2)+1?

Am I missing something (errata?) or is there a misprint somewhere?