On dragging the mouse cursor over the input field of the following properties don't change its value under Mesh Resolution from Terrain Settings in the Inspector.
Properties:
Terrain Width, Terrain Lenght, Terrain Height, Detail Resolution Per Patch, Detail Resolution, Refer the attached video.

Steps to repro:
1. Create a new project
2. Hierarchy > Create > 3D Object > Terrain
3. Inspector > Terrain Settings > Mesh Resolution
4. Change the input value of Terrain Width/Lenght using mouse dragger

Actual Result:
The properties input value under Mesh Resolution is not changing on dragging the mouse over it

Expected Result:
Input value for all properties under Mesh Resolution is change using mouse dragger

Occurring on:
2020.2.0a18. 2020.1.0b16, 2019.3.15f1, 2019.2.13f1, 2019.1.11f1, 2018.4.24f1

Environment:
Occurring on Windows 10 & macOS 10.15