I can't be sure but that looks like one of the quests inside the Red Pants Army fortress (in Korin forest) to visit one of the doors. I never had the XP/Zeni display screw up like that though, which is why I'm not sure.
If it is one of those quests then it should have gone away if you used the dynamite or vial thing to open/break the corresponding door, but will stick around if someone opened it for ya. Do you have either of those items sitting in your inventory by chance?
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