it has an * next to the marriage - indicating that the date is estimated from the date of the first child. I can't see the marriage to James Jacques on the AVRI which includes all the tasmanian records to 1899. What information do you have on your copy of the marriage? Was it definitely Tasmania?
I do have the 1861 marriage which is Robert Wilson 48 married Mary Jacques 38 8 Nov 1861 ref 696
So if this is the same Mary, she would have been about 18 at her first marriage. and born c. 1823. Civil registration started 1838 in Tasmania, so records would be church records only.