The Get-Item value is different from the Item Chart in the way that this value updates when you get close to an item without picking it up. This value has been created by the developpers to make us able to open actors (chests in that case). For whatever reason (please Mzxrules, help me on that one) the value stays positiv if you get close to an item that is not in a chest, (nuts, heart pieces, bugs etc...) but goes negative if you hump a chest. This is why in GIM state, you don't get the item in the chest when you jump into water but the negativ value of this one.