This enumerated/bitmask value lists which additional, non-key fields (such as byte or packet counts) this flow-monitoring record definition includes in each flow record without using them to distinguish one flow from another. An admin adds fields here on this flow-monitoring record definition to enrich the exported flow data with useful metrics (like traffic volume) while keeping the key fields — the ones that determine what counts as a distinct flow — unchanged. A value including 'bytesUsed' would mean this flow-monitoring record definition reports byte counts per flow without using them to define what a distinct flow is.