The numbers are realistsic ...

I haven't found sources for the whole world yet, however the numbers presented are not that surprising given that 2/3 of Western European Muslims can be considered fundamentalist or radical believers, according to a 2013 poll.

The author analyzed data from a representative survey among immigrants and natives in six European countries. Two thirds of the Muslims interviewed say that religious rules are more important to them than the laws of the country in which they live. Three quarters of the respondents hold the opinion that there is only one legitimate interpretation of the Koran.

#... but misused

The key problem in the original statement is the not-so-subtle indication that fundamentalists are all potentially violent terrorists, but that's not how it goes. By the same definition a Catholic nun is probably a Catholic fundamentalist, but not necessarily a commando-style terrorist!

More interesting information which I've found is this document: it has no numbers but it's a really interesting description of all the facets of Islamic radicalization, and you might find it useful: Studies into violent radicalisation -- The beliefs ideologies and narratives