How does ControlNet understands the relationship between the layout map and the descriptive text.?

[ShanZard]

I have a question. When training ControlNet, the first image's semantic segmentation mask values (0, 1, 2) represent the background, the aircraft, and the train, respectively, and the corresponding text also describes these goals. In the next image, the semantic segmentation mask value represents other objects. Is it OK to do so? Or I need some other values to represent new objects. It would be great if someone had done similar experiments

Furthermore, this raises a question about how ControlNet understands the relationship between the layout map and the descriptive text. If the above is possible, then the layout map doesn't really need to represent any semantics, just the spatial layout. On the other hand, if this is not possible, it means that the layout map is better to provide semantic information as well.