You can create two types of seed files: seed DGN files and seed DWG files.
Seed DGN files and seed sheet models are simply DGN files that are copied to create DGN files and sheet models. DGN files can contain one or more design models, drawing models, and/or sheet models.
Seed DWG files are DWG files that are copied to create DWG files. DWG files can contain one design model and multiple sheet models.