Busy == not available?


When i call internal softphones and:
a) destination phone is not available (is not registered)
b) destination phone is busy (talking with other user)

There is no difference between a) and b).
I am always moved +100 priority:

exten => s,5,Dial(${PROTO}/${CALLTO},${TIMEOUT},${OPT})
;nobody available
exten => s,6,VoiceMail(${CALLTO})
exten => s,7,Hangup()
exten => s,106,Playback(custom/number-busy)
exten => s,107,Hangup()

i never gent into ‘nobody available’.
i always (in a) and b) tests) finish in ‘busy’ procedure (hearing number-busy).
Why ?