According to
Simsmx's post in the Hidden Skills thread, after level 5, each level adds a +5 to the "Enjoying Music" moodlet, i.e.
25 - 10 = 15
15/5 = 3
The three equals the skill levels after level five, which brings us to a conclusion that the Sim in question has 8 skill points in the Snake Charming hidden skill.
Since it's a hidden skill, you can't "see" when he reaches level 10, but you can determine if he has already reached level 10 by using the above formula. I.e., when the moodlet becomes +35, you will know that he has maxed out the Snake Charming hidden skill. It's actually very possible that King Cobra will still bite him in the face, I know from my own experience, when I tried snapping this shot during the Photography Challenge.
Hope this helped.