Pay per minute / view - Few minutes trial membership

I am interested in using nimble/wmsauth for streaming website. I would like to give customer a free 10 minute trial, to see if they enjoy the live website streaming content before paying.

I have read the documentation.
"Handler needs to return list of all blocked IDs on every sync. If some ID is excluded from the list, it will be allowed to access."

To me this says, every person in the world can access the stream apart from those who have been added to deny list. Please can somebody explain this with more detail?
I don't understand why it is not an "allow" list just allow those few who have paid for premium website access.

Thanks

first of all: "To me this says, every person in the world can access the stream apart from those who have been added to deny list. " this is not correct. Everyone with valid signature have an access till you explicitly deny some of them. We assumed that allowed client id is bigger set than deny and this is why deny used