See and use Wiyabal E16. Oates (1975:211) introduced a new language code E15.1 and assigned to Wiyabal. However, this assignment is incorrect.
Speaker numbers were measured differently across the censuses and various other sources listed in AUSTLANG. You are encouraged to refer to the sources.
Speaker numbers for ‘NILS 2004’ and ‘2005 estimate’ come from 'Table F.3: Numbers of speakers of Australian Indigenous languages (various surveys)' in 'Appendix F NILS endangerment and absolute number results' in McConvell, Marmion and McNicol 2005, pages 198-230 (PDF, 2.5MB).
Sharpe, Margaret. 2002. Dictionary of coastal Bundjalung : including Bandjalang, Wiyabal, Minyangbal and Ngahnduwal. Armidale, NSW: The Author.