Garmin 530 vs. Garmin 130 | Which gradient is correct?

I am back in the Vosges and brought my 130 with to check and compare the gradient to the 530. The 530 is my go everywhere Garmin as I love the back to start function when I am riding in unknown areas. Unfortunately I have had had some gradient problems with the 530 NOH model, same as with the first 530 and wanted to know what the difference really was. Also i like to know what the gradient is when I am riding in the hills as sometimes my legs feel dead but if i know it's 21% I can relax and I know it's due to the gradient.

athletenatural.blogspot: http://athletenatural.blogspot.com/20...
Komoot: Barry VJ

Who the heck is Barry? I am a ex- elite triathlete and started riding in 1984. In real life I am a chiropractor.
This channel is about cycling and health. I also build my own bikes which can be a risky business as actually i am a chiropractor.
Born and bread in South Africa, riding my bike in The Netherlands is one journey of discovery as it's so beautiful. I race mountain bike marathons and will soon be doing my first gravel race.
I raced as a triathlete in South Africa and the United States of America and was on the South African Triathlon Invitation Team 1989.
Currently i am racing the Sforz MTB Cup in the Netherlands and Germany. I finished in 4th place in my age-group in 2017 and 2018 - 50+
Thank you for watching my channel.
Cheers