Magnus Carlsen lost to Magnus age 14
GM looses to Magnus Age 10
The app is accurate to where he was in real life. He became a GM at 13, so the app at 13 plays at around a low GM level. This means that you probably didn't beat him at age 15 given your current rating on the site.
At 15 he was a 2625 rated player. Maybe you should take this game over to the forum about a 1300 rated player beating a 2700 rated player. If your story is true then you have gotten the closest. However saying it doesn't make it true.
Nothing is embarassing here, it's just a computer engine.
So GM doesn't play 10 years old Magnus , but an engine which rated 2200, 2300 or 2400 which ever rating is there set. Also engine always plays a bit stronger then it's actual rating
How embarrassing