networking - How does delta compression reduce the amount of data sent over the network?

Many games use the technique of delta compression in order to lower the data load sent. I fail to understand how this technique actually lowers the data load?

For example, let's say I want to send a position. Without delta compression I send a vector3 with the exact position of the entity, for instance (30, 2, 19). With delta compression I send a vector3 with smaller numbers (0.2, 0.1, 0.04).

I don't understand how it lowers the data load if both of the messages are vector3 - 32 bit for each float - 32 * 3 = 96 bits!

I know you can convert each float to a byte and then convert it back from a byte to float but it causes precision errors which are visible.