It meant the same as it means now. A surplus is when you have more of something than you need.
In ancient times, they built grainaries to store grains.
money
The ancient egypts ecomomy is based on surplus and crops
Surplus mean excess in business. A business can have a surplus of product in its inventory, which isn't good for revenues.
A surplus account is the accumulation of undivided profits.
Glass was traded as a surplus. They traded it for stone and wood
they would barter it for other goods
Their empire provided a large revenue.
9 = IX in Roman times
they usually mean something from ancient Rome times.
Depends on what you mean by ancient times. A safe bet is Egypt, Babylon, India (Indus valley) and China.
the oldern ciivvilization of eygpt