There is a difference between "theoretical" strata and "actual" or "effective" strata.
A stratum is the intersection of all the stratification variables, which leads to 480 possible strata that are "theoretical" strata.
But in the reality of the officinal world, some strata do not exist, we do not make a selection of strata, but relate this reality.
For example, we do not have any pharmacies with a turnover of more than 3M€ in rural pharmacies in Ile-de-France.
Only the "observed" or "effective" strata, i.e. 132, are retained.
But the stratification model is adaptive, in the sense that if a new stratum appears or disappears, the model automatically adapts to take into account the number of "effective" strata.