The population counter is an estimate and not a real-time representation of how the population is developing. The counter does not immediately go up once a child is born or an immigrant registers, nor does it immediately go down when someone dies or when an inhabitant emigrates. Such events are only processed by Statistics Netherlands after they have been recorded by a municipality. The records are not updated immediately either: a birth is reported to the municipality somewhere within three working days, a death somewhere within six working days, and an immigrant often only registers as a resident after a while.
That is why Statistics Netherlands estimates growth in advance. The basis for this is the provisional population figure on the first day of the previous month, supplemented by the expected growth rate for that particular time of year and day of the week. After all, population growth rates vary from day to day, month to month and year to year; more children are born on a working day than at the weekend, there are more births and fewer deaths in summer than in winter, and immigration is up during August and September.
The counter only represents the registered population and does not include, for example, illegal immigrants or asylum applicants who are residing in the country but have not been included in the municipal population registers.