Read to get variable

In extensions_additional.conf in the context of the pstn trunk put the following

exten => 4929982528,n,Answer()
exten => 4929982528,n,Read(digito,beep,10,2,300)
exten => 4929982528,n,SayDigits(${digito})
exten => 4929982528,n,Hangup

But I am not getting the variable, Why?

Best Regards