How does Armor of Faith scale with ranger levels?

[testlum]

Rangers have a -7 caster level penalty because they only gain spellcasting at level 8. Armor of Faith scales with caster level. When a level 27 ranger casts Armor of Faith, do they gain:

• 15% damage resistance  (5% base + 10% from 13 caster levels below character level 21)
• 25% damage resistance (5% base + 20% from caster level)

[jmerry]

The latter. There's nothing special about level 20 in the underlying mechanics; that's simply the caster level at which most spells stop improving in the BG series.