How many observations will be visible in the output if FIRSTOBS is set to 25 and OBS is set to MAX for a dataset with 40 observations?

Setting the FIRSTOBS option to 25 indicates that the output should start displaying observations from the 25th row of the dataset. Coupled with the OBS option set to MAX, which tells SAS to display all available observations from the dataset starting from the specified FIRSTOBS position, the output will include all observations from 25 to the end of the dataset.

Given that the dataset contains 40 observations, when you start from the 25th observation, there are 16 observations remaining (from observation 25 to 40, inclusive). Therefore, the output will show these 16 observations.

This understanding clarifies why the correct count of visible observations in the output reflects the selections made using FIRSTOBS and OBS.