Its hurting my brain too I wouldnt say 5700xt is 50% as fast I would say its 50% slower. As in 1/2 as fast as a 3080. So 3080 is twice as fast which is 50% faster than a 5700XT. Therefore 3080 is 100% on that scale. If it was 100% faster to me it would be 150% on that scale. Its too late who cares whats right or wrong I'm off to bed.
You need some maths lessons... But I think I see where/why you're going wrong, so maybe this helps.
The 5700XT is half as fast as the 3080, so 50%. In this statement, the 3080 is the reference point.
The 3080 is 50% faster than a 5700XT -- this statement is incorrect, because you've changed the reference point to the 5700XT. The 3080 is TWICE as fast, 200% = twice.. so to get from 100% to 200% you don't add 50%...
Let's use real figures to illustrate this further;
You have 2 numbers, A=100 and B=50
50% of A = 50 (half of 100)
Add 50% to B; you get 75. (half, 50%, of 50 = 25.. add that to the base value of 50 and you get 75)
To make B equal to A, you have to add 100% to B - since 100% of B is 50, so 100%+100% or 50 + 50 = 100.
Basically, it matters what your reference point is.