You are saying there are only 4.2 million mulsims in France?
No.
There are approximately 5 million people of North African lineage in the Republic, which has a population of 62.5 million people. They comprise a bit under 7% of the population.
Of course, everyone of North African lineage is not Muslim, just as every Latin American is not Catholic. Many Beurs are secularized, and don't have a religion at all.