As you know, for files, DPM can store a maximum of 64 recovery points for each volume included in a protection group, and it can create a maximum of 8 scheduled recovery points for each protection group each day. The limit of 64 recovery points for files is a result of the limitations of the Volume Shadow Copy Service (VSS), which is necessary for the end-user recovery functionality of DPM. The recovery point limit does not apply to application data.
This is a VSS limitation which allows up to 512 snapshots to exist simultaneously for the same volume, from which maximum 64 snapshots could be used for the Shadow copies for Shared Folders feature. So the total number of recovery points is limited to 512 for application servers and 64 for file servers.
Here are some good reference materials: