Confusion on SPFileVersionCollection and SPListItemVersionCollection

I have 17 versions on a file uploaded into a document library. When I use SPFileversionCollection, I get 16 versions, while SPListitemVersionCollection shows 17 versions.

I think SPListItemVersionCollection contains draft version whereas the other one SPFileVersionCollection contains only published version.

But why there is a difference in number of returned 开发者_如何学运维versions?

The SPListItemVersionCollection object contains all the versions, including the current one.

The SPFileVersionCollection object does not include the current version.

Documents and versioning