Message Value different when pressing a pad instead of turning its knob

I have a momentary pad control defined as follows:

When I press the pad, the script below prints me the On message value = 3, which is as expected.

function selectIt(ValueObject, value)
local message = ValueObject:getMessage ()
local messageValue = message:getValue ()
print ("message value: " … messageValue )

However, when I turn the physical knob until the pad is engaged, it returns me a message value = 0.
Is that meant to happen?