I main BLM but my secondary job is SCH. When you use Adloquium and heal for 500, you then also put a shield up for 500. Now say you are lucky and crit and heal the target for 700. In this case, whenever you crit on a heal with Adloquium, the shield is double. So, in our crit of 700 example, then the shield is 1400. (Which is why the Crit stat is SCH's most important secondary stat)