72.0.3609.3 (Official Build) dev (64-bit) 
Firmware Version: Google_Cave.7820.384.0
ChromeVox
Steps to Repro:
# With ChromeVox ON,
# Open Settings App from the Status Tray 
# Linear Navigate to any sliders for example Menu>Settings> Devices> TouchPad> Touchpad slider
# Try to increase or decrease the slider with Search Right and left arrow key or search and Up and down arrows to increase or decrease the sliders.

Expected: Sliders should increase or decrease with keyboard strokes without using mouse
Actual: Not able to increase or decrease the slider