Dumb VTA Question

I am confused which SRA angle I should actually. In the original article and subsequent articles measuring SRA with a microscope by Michael Fremer the angle is measured between the horizontal record and and line which runs theough the middle of the stylus. On the other hand, in a recent article in TAS on tt setup by Andre Jennings and other articles/posts in the internet the SRA is measured as the angle between the record surface and the backside of the cartridge. Depending on the cartridge I would estimate thag the difference between the two ways of measuring are approx. 7-10 degrees. Am I misunderstanding something or is the correct angle to measure depending on the type of cartridge (in my case Dyna 17D3)?

Thank you for your quick comments, which I read with some relief as I was not really looking forward to buying a microscope + stand and spending a day or, as I am not really handy with computer programs and all this, several days learning to handle it. \
I think an underlying reason for my question may have been that I am not quite sure what to strive for in my system, i.e. what sound could be achieved in my room with my gear when everything is set up just right and thus form the reference. I get a lot of compliments for the music from friends and other visitors but am sure that considerable improvements could be achieved by someone more proficient than I am.