GFP uses an in-house "Power Index" formula to essentially tabulate and compare
counting stats on a number of publicly available factors that it deems important when assessing military strength. I assume that there is an amount of weighting for the factors themselves.
While having said factors readily available to view on a per country basis is somewhat useful to the reader, trying to use them in any context without the corresponding nuances that accompany them is an exercise in utter futility.
There is no way to derive results of any validity from a quantitative analysis of disparate stats. The reason the the big boys (think tanks and governmental agencies) are paid the big bucks is that they perform
qualitative analysis on the things they want to study.
So in the end, while mildly entertaining in its particulars a survey like this can only be thoroughly flawed.
Case in point, a simple example. Below is a naval analysis between two random countries, Poland and Greece.
The GFP formula assigns an overall "Fleet strength" number, derived from the (assume weighted) analysis of counting stats in some (not all) naval ship classes. The formula somehow manages to give a
87 to 116 fleet power stat when comparing the two navies, without of course providing any qualitative analysis for the classes it counts. And if one could wager a guess, a good chunk of Poland's fleet strength as shown is derived from the large number of....minesweepers it has.
For a more direct comparison, try to view these two pages.
List of ships of the Polish Navy
List of active Hellenic Navy ships
Now, try to assign a comparative fleet power between those two navies yourself. I think you are going to reach a very different conclusion. And that conclusion would ALSO be thoroughly flawed, because you are missing things like naval airpower, training, availability, roles, context of use etc etc.