Numerous taxonomic systems have been developed over the years that have used different characters to separate genera into families. Previous releases of the Angiosperm DNA C-values database generally used the family name given by the author(s) who originally estimated the DNA C-value. This is referred to as the "TRADITIONAL" family and is displayed on the Results page if you select this option.
The Angiosperm Phylogeny Group (APG) has combined new molecular and non-molecular phylogenetic data to release a revised classification of angiosperm families (APGIII, 2009). Selecting this option on the query form will give the family name recognised by the APG (=APG family) for a particular genus. Since the APG classification has resulted in changes in the circumscription of some families (e.g. some families have been sunk within others) the "traditional" family name may be different from the "APG" family and thus the outcome of the query will be different.
APG III. 2009. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG III. Botanical Journal of the Linnean Society: 161: 105-121.