A reserve is the floor the consignor sets. If bidding doesn't reach it, the lot goes no-sale rather than selling under reserve. Reserves are optional — many lots have none and sell to the highest bid.
The reserve is quoted in the lot's pricing-mode unit: dollars per cwt for a per-cwt lot, dollars per head for a per-head lot, or a total for lump sum. Setting "1500" on a per-cwt lot means $1,500/cwt, not $1,500 total.
Technical section
Data model, API, and internals — visible to developers.