We have fixed a mistake with the UMProvider (OAI provider) that caused there to be more Dublin Core format records than MARC format records. This was due to our not implementing the "deleted records" function for the MARC records. There were about 1500 of these-- a re-harvest will grab these now-deleted records (e.g., records that had their rights status changed to in-copyright). We apologize for the inconvenience.
We have also discovered that there is still a discrepancy of about 1800 records between the number of records in the provider and the number of records in our HathiTrust databases. This is partially due to the fact that the provider is a day or two behind the databases. We will keep an eye on this discrepancy, as this is only a partial explanation.
As of today, there are 391,640 HathiTrust records (not volumes) in the provider and 882,409 total records.
Please do let us know if you have questions or comments about the provider. We're interested in how others are using it.