Yes, it's normal calls that aren't answered. Instead of going to VM, it goes to the failover number.

The other thing I've noticed is that if you set the number of rings to a high number (say 10), it seems to ring for a "maximum" of 30 seconds. After 30 seconds, the call is interrupted for a very short time (less than 1 sec), and then it starts ringing again. Looking at my Asterisk CDR's the incoming call looks like multiple failed calls. To be more specific, if I let the incoming call ring for over 60 seconds (who would do this? except, of course, someone looking to leave a voicemail message), my CDR's show three failed calls. The first two are 30 seconds in length, and the third is whatever past the 60 seconds I let it ring.

One of my extensions is an IP phone, and I can see the incoming call 'stop' briefly between the 30-second "cycles".