Option string question

Im having a little trouble getting my head around the option string structure.
Im trying to add a option to the sales line type option string.

Here's what i did:

Option string: [ ,G/L Account,Item,Resource,Fixed Asset,Charge (Item),,,,Item2]
Option Caption: " ,G/L Account,Item,Resource,Fixed Asset,Charge (Item),,,,Item2"
Option CaptionML: ENU=" ,G/L Account,Item,Resource,Fixed Asset,Charge (Item),,,,Item2"

*I left some space for possible expansions etc.

Result: Nothing, i don't see the "Item2" option.

So i tried the following:

Option string: [ ,G/L Account,Item,Resource,Fixed Asset,Charge (Item),,,,Item2]
Option Caption: " ,G/L Account,Item,Resource,Fixed Asset,Charge (Item)
,placeholder,placeholder,placeholder,Item2"
Option CaptionML: ENU=" ,G/L Account,Item,Resource,Fixed Asset,Charge(Item)
,placeholder,placeholder,placeholder,Item2"

I replaced some of the ,, with placeholder text.

Result: I see the option but i get the following error message:

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Microsoft Dynamics NAV

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'9' is not a valid value. The following values can be used: ,G/L Account,Item,Resource,Fixed Asset,Charge (Item),,,,Item2.

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OK

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Any ideas where i forgot my thinking hat?