Hi,
In power_profiling.c you can find that the advertising type is set to slow advertisement (slowAdvState_c), inside the BleApp_Start function.
When slowAdvState_c is selected, the BleApp_Advertise function sets the advertising interval time to the value of the gReducedPowerMinAdvInterval_c macro:
gAdvParams.minInterval = gReducedPowerMinAdvInterval_c;
gAdvParams.maxInterval = gReducedPowerMinAdvInterval_c;
The definition of this macro can be found in power_profiling.h and while you can modify its value, please be aware that you should use the pre-defined time intervals to comply with the BLE time specifications and constraints and ensure the correct behavior of the application.
Regards,
Eduardo.