The height of the gNB is a user-defined value. When the chosen scenario is Urban Macro, the height of the gNB that a user would typically enter is  25m, which is the value provided in the standard. However, NetSim doesn't strictly enforce this 25m value. 

This means that a user can enter a different value. Based on the value entered NetSim would calculate the path loss per the following set of equations.

When the input to the h_BS is entered as 40, it overwrites the default value of 25 (hence for the calculation of pathloss h_BS is taken as 40m). The d3D parameter which is used to calculate the pathloss in LOS and NLOS depends on the hBS value. Therefore the values of pathloss depend on the user input hBS value.

For more details, pleaase refer to Table3-23: Pathlossmodel fromStandardsTable7.4.1-1. in 5G manual - https://tetcos.com/downloads/v15.0/5G-NR.pdf