Height and Width have the following interpretations:
Non-negative values indicate a specific pixel value for the dimension.
For negative values, there are three potential interpretations. -1 indicates Automatic, -2 means Fill Parent, and values < -1000 are used to encode percentages, e.g. 75% = -1075.
For any property in App Inventor, we don’t store the value if it is the default value. This keeps the files smaller, which decreases the time to load/process/save files.