How do I check the size and weight of a cargo container?

When I click on it I got the info
Cargo Stats:
Weight: 50 kg
Volume: 1.0 m³
Weight Cap: 45 kg
Volume Cap: 8.5000 m³

but when I actually load it to my ship, it occupies 4 m³.

The weight defintely corresponds to the items inside, but I always thought that the volume was 1 m3 and was the reason batch sizes varied as they had to fit inside that to a degree. But if you say it takes up more space, then maybe it too takes the volume from the items inside.