You need to used the Generic name of the field in the citation template which for Document number is Number.
You may also need to adjust the Anonymous Work setting in the style to Leave Author Blank since the setting it appears to be on is to use the Title field when a reference does not have an Author.
For additional help with output styles I would suggest that you contact Technical Support.
1-800-336-4474 option 4 then 1
or
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