bubble, bubble, but not in trouble

I'm getting very keen on fermenting and have a book called The Complete Idiot's Guide to Fermenting. Monday I mixed up some kimchi and got it into jars. Starting on the third day you're supposed to burp the jars twice daily. This is what I found:

If your finely chopped fermented food is simmering wildly in the jar, don't be alarmed!  As long as it smells okay, it should be fine.

I am not an expert, but this is what I was told. You see, it happened to me once before.