Microsoft Knowledge Base Article 842355 contains the following summary:
Microsoft Windows Server 2003 Services for Macintosh allocates system resources for each Macintosh file and folder that it shares. Services for Macintosh also allocates resources when it rebuilds the index of a Macintosh volume. Some of these resources are shared by other kernel components. This article describes the resources that are allocated to each file and folder on a Macintosh volume. You can use this information to help plan how you set up your server.