What do the numbers in 3 * 4 * 1.5 (6) mean?

What do the numbers in 3 * 4 * 1.5 (6) mean?


Three phase four wire ammeter, rated current 1.5A, maximum current 6a, generally used with CT



Mark "10 (40) a" on household meters,
"10": the calibration current is 10A
"40": the maximum current is 40A
On the premise of safety, the maximum allowable power is:
220 V × 40 A (max) × power factor 0.9 × 3 phase = 24 kw


When the appliance works normally, the current passing through is 10a, and the maximum current allowed to pass through is 40A