From a grid perspective, the output (delivery) is typically more important than total capacity - because it's acting sort of like a power plant.

Power plants don't have capacity, really.

So you hear about the output GW, not the capacity GWh.

For battery plants, they might mention duration (4 - 6 hours), which makes converting to capacity in terms of GWh trivial.

90 GWh would be something like 10% of global annual battery production.