Just guessing that you were... 30 inches off the ground...
20 Degree ramp score: 831 you would have traveled 87.7 inches
30 Degree Ramp score: 569 you would have traveled 60 inches
That ramp looks more like 40 to me.
which would translate out to: 442 you would have traveled 46.6 inches
Those figures might get you a ball park if you try to figure out just how high you were and how far it appears you made it up the ramp...
I am guessing you got your wheel 24 inches high
and you probably traveled 30 inches. which is making the calculator show that ramp at being closer to 40 degree, it's hard to tell from the picture, if you can find out how far you can get your tire in the air before any other tire comes off the ground... we can ballpark it for any angle ramp.