Gauging wattage with a kick

Alright so I got my kick in the mail yesterday. It’s awesome! I have no idea how to gauge where I’m at though. It’s a singelie one. There are 8 indicator marks, but the website says it’s from 5 to 15 watts. Have you guys come up with a method to figure out where exactly you’re at with it? Also, is the rattlesnake noise a bad thing? It doesn’t really bother me except that it makes me a bit uneasy since I don’t know if it’s normal.

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