The explanation for this is quite simple! The reason for the difference is because the measurement that is provided from these sources are based at sea-level. This provides a baseline measurement to work from that can be adjusted based on your elevation. The higher the elevation where you live, the lower the air-pressure will be. Additionally, temperature and indoor mechanical ventilation can also play a role in your indoor air pressure levels.
Here is a helpful calculator that you can use to understand the change in air pressure with elevation: https://www.omnicalculator.com/physics/air-pressure-at-altitude