This is a numeric board-type code recorded in the capability catalog, corresponding to the PROM (identity chip) type that a rack server's motherboard reports, which UCS Manager uses internally to confirm it has matched the physical board to the correct capability record. An admin wouldn't normally read this value directly, but a mismatch between the PromCardType a real board reports and what a capability record expects is a common cause of a server showing as an unrecognized or unsupported equipment type in UCSM. Different rack-server board revisions typically carry distinct PromCardType codes even when their marketing model number is unchanged.