Sometimes number sequences do not advance as they should, especially when set to 'Continuous' under the General tab in Number Sequence setup. I've seen this behavior with Journal Batch numbering more than any other number sequence type. Here's how to resolve this quickly and easily if it occurs.
Navigate to Organization administration >> Number sequences >> Number sequences and select the offending Number sequence. Then under Administration, select 'Status list'.
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Delete any records that appear in this list. No Edit or Delete button you say? Not to fear - type Alt-F9 (the keyboard shortcut for Delete in AX). Voila. Problem solved. Go back and try your journal again.