why VCM scanner read wrong spark advance????

[Paoloz]

I got in this issue with my E38 LZ4 from an impala 2009

in VCM scanner reading spark advance [sensor] at high revs and high load I never read more than 24?...............

Then I did some test (disabiling correction etcc......) and at the end i discovered that is not true........infact if I put 30? in the map in this area I read 30? in base cyl1 advance with no correction, and I clearly notice a starting of detonation (so definetely spark advance is increased) but in spark advance sensor I alway find 24?

It's a big mystery do you have any Idea?
should i read a different spark advance?

Paolo

attached map and log