I'm curious to know if this is a lot? Average? I personally don't know anyone with a dog who also has seizures to ask them how often is too much or I'd ask them.
I don't know that there is an average -- or an acceptable number. I know when my own dog started having seizures my whole goal was to keep them to a minimum, but I had no idea what that number might be. Personally, I'd like to see less than 3 times a month, but I don't think it works that way.
It is alot. I had an epileptic cat years ago, she was on phenobarbital and for a long time it kept her seizures at bay, she'd maybe have one once every 2 months. But toward the end she started having multiple monthly, within less than a year she had to be put down. She had a seizure that wouldn't end and we had to take her to an emergency vet and that was it.