Too much math snark for their own good.
All right, since everybody is being too clever for their own good...
The idea of a daily limit is pretty simple: some nations had a limit that was under the 12 minutes per hour. That meant that if the ad blocks were 12 minutes, one per hour, there would be a few hours without any ad blocks, but the size of the ad blocks could not exceed 12 minutes within one hour.
So the whole upshot is that they are saying that since they are already limiting per hour, an extra daily limit is moot. Just 12 minutes maximum within an hour. No 18 minutes in one hour and 6 the next. 12 is all you get until the next hour begins.