Does Simulink block metric includes count from custom library blocks

The documentation of Simulink Check Model Metric says Simulink block count

Does not include links into MathWorks libraries, which means that MathWorks library blocks 
that are masked subsystems are counted as one block. The inner content of those blocks is not counted.

What are Mathworks LIbraries ? Does these libraries also include user created custom libraries?

Answer 1

[Pat Canny]

This refers to blocks developed by MathWorks, and not custom libraries.