Vax part 2?
It’s just math.
For it to be greater than 100%, the shingles would have to be cooler than the ambient temperature. I think that is what is meant. If it’s 23C and the shingles are measured at 21%, they’ve passively cooled whatever it is that they are covering.
It’s possible that it is doing that. It’s just a question as to whether it is worth the cost and the negative. It’s going to cool in winter temperatures as well, so are you going to lose during winter when you may have to run your furnace longer to make up for the additional heat lost by these shingles?