No not at all.
What it means is that instead of 6 hours sleeping and 2 hours of light activity during a long rest, you have 4 hours of trance and 4 hours of light activity.
Long rests for everyone are 8 hours.
You can only take one long rest in any 24 hour period.
Sage Advice "Trance" as search term http://www.sageadvice.eu/?s=trance
Hooray another horribly written rule.
I'm going to stick with how it's written in the book, an elvish "long rest" is 4 hours.
Perfectly fair; I prefer to go with that, too. (That is, I don't require another 4 hours of "light activity" only.) But the book does not say or even suggest that the elvish trance breaks the "only one long rest in a 24-hour period" rule, which I think is the more relevant point.
Actually, if you go by RAW (an idiotic notion), then Elves can't Long Rest without doing nothing for 2 hours.Play it however you want. But don't blame it on the book. It is written the way it is supposed to work. I can understand potential confusion, but it is correct as written.