How to reproduce:
1. Create and open a new project
2. Create a UI Document and open it in UI Builder
3. Create a new USS StyleSheet inside the UI Builder
4. Create a new “.test“ class in the StyleSheet and select it
5. In the UI Builder’s Inspector, change the Position > Top and Right to “0%”
6. Save the Changes
7. Open the USS StyleSheet in a text editing app
8. Create a new line below the fields in the USS StyleSheet and save the changes
9. Select the “.test“ class in the StyleSheet and observe the Inspector > Position

Expected result: The “%” symbol is still displayed
Actual result: the “%” symbol is changed to “px“

Reproducible in: 2022.3.59f1, 6000.0.41f1, 6000.1.0b9, 6000.2.0a6

Reproduced on: Windows 11 Pro (24H2), Linux 6.12.11 (By the user)
Not reproduced on: No other environment tested

Note: This only happens if the serialized values are 0