To reproduce:

1. Open Unity and create a New Project
2. Create a new script and attach it to any gameObject
3. Open the newly created script and paste these lines:

[Header("Smoothing. Set iterations to 0 to disable. ")]
[Header("Smooth Iterations (CPU loop)")]
[Range(0, 50)]
[SerializeField] private int SmoothIterations = 1;

4. Save the script and go back to Unity Editor
5. Select gameObject on which attached script is and inspect it on Inspector
6. Observe that the Script component renders the Headers in reverse order

Notes:
- This issue happens on both Windows and macOS
- Image for reference is attached in Comments section

Reproduced on Unity 2017.4.0f1, 2017.4.32f1, 2018.3.14f1, 2018.4.7f1, 2019.1.14f1, 2019.2.3f1, 2019.3.0b1 and 2020.1.0a1