Last month, sodium-ion battery manufacturer Natron Energy announced it would open a "gigafactory" in North Carolina that would produce 24 gigawatt hours of batteries annually, enough energy to charge 24,000 electric vehicles. But sodium-ion batteries are still early in their development compared with lithium-ion, and they have yet to hit the market on a massive scale.
The word "charging" shouldn't have been used at all here. It implies that the factory is going to be producing energy when instead it's going to produce energy storage devices.
It's like confusing petrol with jerrycans.
The Tesla model S battery pack is 60-100kWh (depending on option chosen, YMMV)
24gigawatt hours == 24,000,000 kWh.
24,000,000 kWh / 60 kWh = 400,000
24,000,000 kWh / 100 kWh = 240,000
It's unclear from the "article" but it seems that the factory is currently in the planning stage, and is expected to take 12 years to build, once they finish designing it.
In other words, when completed (in 12-15 years), they project that the factory could produce enough batteries to equip 240,000 - 400,000 EVs every year (if it ran at maximum capacity 24/7)