Dear Stata users,

After applying svyset command to dataset with weights included in the dataset and 15 stratas generated considering sample design:
Code:
svyset cluster [pweight=weight], strata(strata)
I am getting a result of
Code:
svy: mean bcg
with population size smaller than the number of observations.
Code:
Number of strata =      15        Number of obs   =        622
Number of PSUs   =     336        Population size = 613.447816
                                  Design df       =        321

--------------------------------------------------------------
             |             Linearized
             |       Mean   Std. Err.     [95% Conf. Interval]
-------------+------------------------------------------------
         bcg |   .9828574    .008315      .9664986    .9992163
--------------------------------------------------------------
Would you be so kind to have any suggestion what can possibly be wrong in that case?