Wall of Fire reads (emphasis mine):
An immobile, blazing curtain of shimmering violet fire springs into existence. One side of the wall, selected by you, sends forth waves of heat, dealing 2d4 points of fire damage to creatures within 10 feet and 1d4 points of fire damage to those past 10 feet but within 20 feet. The wall deals this damage when it appears and on your turn each round to all creatures in the area. In addition, the wall deals 2d6 points of fire damage +1 point of fire damage per caster level (maximum +20) to any creature passing through it. The wall deals double damage to undead creatures.
If you evoke the wall so that it appears where creatures are, each creature takes damage as if passing through the wall. If any 5-foot length of wall takes 20 points of cold damage or more in 1 round, that length goes out. (Do not divide cold damage by 4, as normal for objects.)
If you cast a Wall of Fire down the middle of a huge creature, per the second paragraph it would take damage as if passing through. However during its turn it cannot 5' step "escape" because of its size (cannot 5' move to the heat side or 5' move to the non-heat side), so does it take the passing through damage a second time if moving out?
I feel like the general D&D intent is generally for spell effects to happen once a round but I cannot find any ruling that states that explicitly or contradicts the taking of the damage twice in this scenario.