The template in citation should be (Author, Year|:Cited Pages|) and should have no effect on the number of authors showing, at least for first appearance.
However, if it is the second time that citation is listed rather than the first, the Citation: Author Lists setting in the output style may be different as it could be 4 or more list 1 for first appearance, and then 3 or more list 1 for Subsequent Appearances for example.