New installation - how to adjust the pressure "Aqara temperature, humidity and pressure sensor"

As a new user I installed Home Assistant as a virtual machine on my Synology NAS. An Aqara sensor is connected via zigbee2mqtt and is working. Unfortunately, the sensor is located at a higher altitude. The reading of the pressure is 851 hPa but the corresponding local pressure should read 1020 hPa. How to adjust the reading either by adding the difference of by using a formula? Thank you.

Unfortunately, this post does not help me.

Why not? It instructs to create a proxy template sensor that you can use to calibrate the original sensor value by using any math you want. Adding or multiplying or anything else you require.

Thank you for your support. I could fix it with the following post: Add Xiaomi Temperature and Humidity Sensor