How to weigh the size of a spatial event with respect to the number of its hotspots?

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This is probably a map algebra problem. I have a 2D map with values ranging 0.0 to 1.0 spread all over it. The algorithm that produces them is an application of the fractional Brownian motion. The map measures 101x101 pixels or cells.

My problem: I want to find in the map the regions (or islands) which values exceed a given threshold, e.g. 0.3 (we can call them the hotspots). I then want to calculate the number of pixels or cells that fall within the boundaries of that island. Given that there might be more than one island, I could end up with:

1. Situation 1: 1 island with, say, 1000 pixels or cells;
2. Situation 2: 2 islands with 500 pixels or cells each;
3. Additional combinations.

Since I must be able to distinguish between the two situations, I was thinking of somehow weighing the total number of cells with respect to the number of islands. How could I do this, if I don't want to consider the average number of cells?

Below is a visual example of what I mean by islands or regions.





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