This policy setting limits the number of files that a BITS job can contain. By default a BITS job is limited to 200 files. You can use this setting to raise or lower the maximum number of files a BITS jobs can contain. If you enable this policy setting BITS will limit the maximum number of files a job can contain to the specified number. If you disable or do not configure this policy setting BITS will use the default value of 200 for the maximum number of files a job can contain. Note: BITS Jobs created by services and the local administrator account do not count toward this limit.
Network\Background Intelligent Transfer Service (BITS)
At least Windows Vista