As I mentioned in the Explore forum, the altitude indicated by the app is wrong. It is the Ellipsoidal altitude and not the Orthometric altitude. The difference is very important: approximately 50 meters more or less in Spain, varying according to the area of the earth.
Today I have seen that when a message is sent from that app, the transmitted altitude is wrong.
However, the altitude reported by the inReach M2 in Navigation and attached to a message sent from that device is correct.
The difference is big and can cause a rescue team to be looking for someone at a different altitude. You can check it by sending a message from the app and from inReach, in a clear place