RPM in the AdSense system means page revenue per 1,000 impressions. That's just a statistical measurement of that click/impression, a way to measure the value of that click versus other clicks in different parts of your site. So if one ad unit is earning a higher RPM over another, it's simply a different data point to consider when optimizing your ads on a sitewide/page/section of page level.

It's a £1.06 click, that's the important part.

Make sense?

Revenue per 1000 impression or RPM is a standardized measure of earnings. Simply put it averages out the earnings across all your impressions for the specific feature you are measuring. In your case it was by country NZ, for the day. It reports the average * 1000, so per 1000 impressions, because otherwise number reported would very small and awkward to use.

To answer the question, the reason it reports an RPM or $1000 for a single click of $1.00 is that there was only one impression since that click occurred. So the average earnings = $1/1 impression = $1 and then $1 * 1000 impressions = $1000. If a few minutes later in the day there is another impression (from NZ) but you earn $0 then the average becomes ($1 + $0) / 2 impressions * 1000 = $500. By the end of the day you had 1000 impressions and only earned a 1$ you would have an RPM of 1$.

This is why one often observes very high numbers reported early in the day for the daily reporting and then one watches the number fizzle as the day progresses. Some claim that it is Adsense throttling their accounts, but it is simply a side effect of how the stats are calculated.