Two Sliders are present for "Size" and "Opacity" for Painting details on terrain

Steps to repro:
1. Open attached or create a new project
2. Hierarchy > right click
3. 3D object > terrain
4. Select paint details from tab
5. Observe the brush size property

Actual Result:
1. On changing the value for "Size" slider other slider's value gets updated too
2. Opacity sliders are independent of each other. Opacity under the "Brush Setting" doesn't effect opacity

Expected Result:
1. Thier should only one set of sliders to edit the opacity and size of the brush

Occurring with:
2018.3.0a6, 2018.3.0a5, 2018.3.0a4

Note:
New Terrain tools are introduced from alpha 4

Working with:
2018.3.0a3, 2018.2.0f2

Environment:
Windows and Mac