Cannot complete Hikari's quest

This is the one very strange quest where the quest helper (which is usually right, even if the text is wrong) is wrong along with the text. You need 10 more than is stated to complete it.

The explanation to why does this happen is pretty simple, though. Quest data splits into two main parts in Quest.wz: Check.img and Act.img.
Check.img specifies what conditions are required in order to finish the quest (Level, day in the week, start\end date, specific items, prequests, etc). The quest helper directly relies on this data, and only on this data.

Act.img is the act needed to be done when you actually finish the quest. A typical "Act" data block specifies you need to remove all the required items from the user's inventory (e.g. if check had "50 snail shells", act usually has "-50 snail shells") and than give the rewards. Although Act.img is contained inside Quest.wz, it almost has no purpose in the client and most of it's data is used by the server.

What happened in this quest, is that Check.img specifies you only need 40 cucumbers (hence why the quest helper shows 40), but Act.img specifies you need to take 50 cucumbers from the user's inventory ("-50 cucumbers"). The server tries to take 50 cucumbers from someone who only has 40, and it throws a common "item inventory is full" error. This error is thrown for almost any problem that occurs inside inventory functions, and also serves as an anti-hacking method (the way it looks to the server, you edited the wz files to make the quest require less cucumbers).