After reviewing this further, it appears that the source of the mismapped data is that the original 15 Custom Fields you had in your account have been renamed. While there is no issue with renaming these fields, each of those fields will stay associated with the original field name for the purposes of API imports.
The easiest way to verify the mappings between the old Custom Field numbers and the current names is to perform a contact import that places an idetifier (Such as CF1-CF15) as the value of each custom field. You can then view the contact was that imported and verify which fields are mapped to which names.
If you are still having any trouble, please let us know!
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