Pana was just making sure that his control over the shadows is solid as he tried to enhance his bow using it. The shadows latched onto his bow, and it suddenly became a long bow that could shoot at high altitudes and long range. He then made sure to also enchant the arrow as he needed to make sure that it will fly that far without losing momentum.
He aimed at the Goddess of Light Luminaria just to test it out. He did not even think that he would be able to hit her with that arrow as he believed that the barrier would just block it like other projectile attacks. With great precision, Pana released the arrow, and it flew at an incredibly fast rate.