Actually, current speculation on the Statblock thread is that the Ability Scores work as normal, and the modifiers listed include a 1/2 level bonus to skills/ability checks. Sort of a Variation on the Saga Skill system.
Primary evidence of this is that +4 Damage on claw Attacks and +2 Damage on the ranged attack mesh easier with a +4 Strength bonus than a +7.
The only skill listed on the Statblock is Spot, which is +10. If you work off the assumption that the Devil has +7 to strength related skills and +5 other skills usable untrained, 5 +5 for perception would give the +10 total for Spot.
The main tricky thing with the statblock is that regardless of which set of ability scores you use, the fact that it's ranged attack equals it's melee attack suggests it has an unlisted bonus to range, penalty to melee, or both.
Edit. Doh! Dragonblade beat me to it. Next time DB, next time...