Pricelisttype 'O'?

I only have 3 pricelists in the pricelists table in the synch manager but when the synch runs I end up with hundreds of rows in the PartsPricingMaster with a PriceListType of 'O' and this translates into thousands of extra rows in the PartsPricing table which ends up timing out the next pricelist synch.

Where do these come from and how are they used in Netpoint? Are these just prices that have been overridden?

Thanks,

Steve