[raminassemi]

Could you explain a bit more how this works?

I think the most important factor would be quality of the subscribers / how good a fit they are for what we're offering.

Also, I noticed this seems to be just about the "first 100"?

Or can this also be used when you already have a larger list?

[boldpanda]

Yes, can be used when you have a larger list.

Quality will be better than average because it will be only topic interested subscribers.