At current gold prices, a discrepancy of ten milligrams on a single transaction is real money — and across a year of trading it compounds into a serious sum, in either direction.
Gold balances read to 0.001 g (one milligram). At that resolution, air movement from a ceiling fan or an air conditioner visibly disturbs the reading — which is why serious gold balances ship with a draft shield, the transparent enclosure around the pan.
Placement matters as much as the instrument: a stable, level counter away from vibration, direct sunlight and vents. Warm-up matters too — give the balance a few minutes after switch-on before the first weighing.
Calibrate on a schedule with the supplied reference weight, and have the balance professionally recalibrated at least annually. For gem trading, a dual-unit carat balance (0.01 ct) saves conversion errors between grams and carats.