Finding AeT via a gas exchange test

I have read both of Scott’s book and bought one of the training programs. The one thing I always struggle with is defining AeT - so I went and did one of the gas exchange tests. Now, obviously the purveyors of these tests focus on Max Vox - but you get all the output and the sheet still give you an AeT number - I guess my real question because even that was somewhat confusing should I be looking for the level where you get to 50/50 fat vs carb usage? Interestingly it was a higher BPM than what the output said (the AeT seemed to settle around 80/20 fat/carb usage) I had hoped to solve my confusion of the original nose breathing test and now even more confused - the data did from the first one 6 months ago AeT was 123BPM and now 131BPM on 2nd test. But the 50/50 point was 143bpm then and now 144BPM - just trying to figure out where my zone 2 training should be at? Some of the data suggests I have barely improved after 6 months but I know I’m faster and doing higher incline % for the same heart rate which tells me whatever I’m doing is doing something but I have a 7000m objective in 4 months and want to make sure I’m optimizing my training