Understanding Elevation Gain in the Health App

Hi, I have just walked to and from my sons house. On the way there the health app says Elevation Gain: 118ft, Elevation: 275ft Max, 131ft Min. On the return walk the app reports Elevation Gain: 244ft, Elevation: 324ft Max, 144ft min. I did not return by the same route.

I know from checking many online map tools that I live about at about 260ft and my sons house is at about 125ft.

So am I misinterpreting the data or is my Apple Watch Series 7 just plane wrong?

Thank you for your help.