meant to say at the end, can't conclude that some NYP are /EG (NYP ←s→ /EG)

Making a visual helped me understand this! Maybe this would be helpful for you too.

All violinists at the New York Philharmonic know how to play the violin. Most people who know how to play the violin are not exceptionally good at playing the violin. Therefore, some violinists at the New York Philharmonic are not exceptionally good at playing the violin.

Premise: NYP → PV ‑m→ /EG

Conclusion: NYP ←s→ /EG -- invalid conclusion, some violinists at the NYP could be not exceptionally good at the playing the violin, but they don't have to be.

The visual below shows how it's possible for NONE of the violinists at the New York Philharmonic to be not exceptionally good at playing the violin. Since none is possible, we can't conclude that some NYP must be /EG.

VISUAL:

Imagine there are 3 violinists at the NYP and 7 people who play violin (PV).

All 3 NYP can PV (3 of 7 people)

Most who PV are not exceptionally good (/EG) - 4 of 7 people.

In this example, it's possible for NYP and /EG to not cross over, as shown below.

NYP PV

NYP PV

NYP PV

PV /EG

PV /EG

PV /EG

PV /EG

Possible for some NYP to be /EG but not guaranteed, can't conclude that NYP /EG because could be none.