Happen to know the breakdown from a percentage basis?
There's not really a great way of estimating that, even at a very rough level. The stats that FreeNAS "phones home" with are pretty limited, naturally because iX wants to respect the privacy of its community members.
We'll do a bit of digging to try to come up with an option for you to effectively try out Asigra's service, but it's fair to say that their license enforcement system is geared more towards businesses since it relies on a static IP. I'm hoping that maybe with a dynamic DNS address pointing to your home IP, we can make something work.