The batch settlement screen filters documents based on various parameters that are specified in step 1 of the wizard - however, there are also a few 'hidden' requirements that must be fulfilled for the document to show up.
One-time documents are shown, provided they have had credit card details associated with them.
These documents will always be settled against the one-time card that is associated with it.
For BP documents things are a bit more complicated:
The BP must have a default card specified, even if the document you're trying to settle has a prior authorization. We do this in case the user would try to settle an amount greater than the prior authorized amount - in which case the default card is used for the remainder.
If a document has no prior authorization, it will be settled against the default card for the BP.
If a document has one or more associated authorizations, these will be settled against the cards that are associated with each authorization - and any remaining amount will be settled against the default card.