Default 4.3 Sleep mode and 4.2.2 Sleep Mode

Just updated to 4.3 on my HTC one.

I am glad HTC nows allow us to manually set the Sleep time (to turn off data)
However, i dunno how to turn the feature "on"

in 4.2.2 We turn on Sleep mode by clicking On
In 4.3, When i turn Sleep mode OFF, i can set the time manually or "Learn sleep mode"
however, when i turn Sleep mode ON, i cannot set anything.
So am i suppose to leave it ON or OFF?