Dhiyakuy is listed as a language in Shebeck (2001:15) affiliated with the clans Wagilak N106; Manggurra N129 and Ritharrngu N104. The name Dhiyakuy is constructed with the demonstrative 'yakuy (this)', but it is not a name recognised by Yolngu. The online Yolngu Matha Dictionary describes Yakuya (Dhiyakuy) as a language group comprised of Ritharrngu N104 and Wägilak N106. See and use Ritharrngu N104. For Yolngu language groups see Yolngu Matha N230.
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).