Hi,
Here's what is written in Vol. 1 about Donald McBain:
"#4884 McBain, Donald. b. ca 1823 PROB from INV(erness) To Erin Twp Wellington Co. <1847; moved to Arthur Twp, Went later to Oak Hill, Victoria Co. Schoolteacher, storekeeper, miller and farmer. m. 4 September 1850 Catherine Turner 1832-1915, ch: 1. Duncan, 1852-1931; 2. Jessie, 1855-1941; 3. Sarah, 1859-1951; 4. James Turner, 1861-1945; 5. Donald Turner, b. 1863, d. Everett, WA. 6. Kathie Edna, 1865-1940; 7. Mary Ellen, 1867-1942; 8. John Arthur, b. 1869, d. Julian, CA; 9. Christina Isabella, 1872-1955. DC* 27 MAR 1979."
*"Dictionary Correspondence. Letters to the author regarding emigrants to Canada contained in 9 lever-arch files."
There are no other code numbers listed in the book, other than the reference to DC. So, the Source Publication Code 9758 must be relevant only to the Ancestry index.
I hope this information is helpful to your research.