Okay, kiddo, let me explain net tonnage to you. Imagine you have a toy boat, and you want to know how much stuff your boat can carry. The weight of the boat itself is called the gross tonnage. But we also need to consider the weight of things like people, cargo, and fuel that the boat can hold. This weight is called the cargo capacity or the net tonnage.
Now, to figure out the net tonnage of the boat, we need to subtract the weight of some parts of the boat that doesn't carry any cargo from the gross tonnage. These parts include things like the engine room, the crew's quarters, and the navigation area. To make it simpler, we can say that the net tonnage is the measurement of the actual space that's available to carry cargo.
So, if we know the gross tonnage of the boat and have subtracted the weight of the non-cargo parts, we can find out the net tonnage. And this is important to know because it tells us how much stuff the boat can carry and how much it can earn for carrying that stuff.
I hope that makes sense, little one. Let me know if you have any more questions!