The seriesid is used to specify a group (or series) of documents which are related. For example, multiple versions, formats, and translations of a single document are considered to be in the same series. Thus, any new version, translation, etc. of a pre-existing document should inherit the seriesid of the original document. Only document series which have never been assigned a seriesid in the past should use scrollkeeper-gen-seriesid to obtain a new seriesid.
ScrollKeeper uses the seriesid of documents to identify which documents are related to each other. For example, when creating the contents list, ScrollKeeper must identify if two documents are in the same series in order to display the most complete set of documents on the system, using locale fallback for documents which may not be translated into a given locale, without displaying the same document in two locales.