Dial parameter L

how to use dial parameter L?
i write an extension as fellows :
exten => _XXXXXX,1,dial(IAX2/${EXTEN},90,L(6601000:601000:201000))

but i dial 222222 for example ,the 222222 can ring but when the 222222 answer it .they will both hangup. i saw the iax2 debug say cause code is 16.
what 's this mean? how to solve the problem?

Have you tried to see if it works in this form

exten => _XXXXXX,1,dial(IAX2/${EXTEN},90,L(360000:60000:20000))


yes ,you are right .they can work .thank you very much.