I-94 and visa waiver time limits

[Shake]

I recently entered the US under a visa waiver and was given a 90 day limit (Dec 12th) for my stay. If I were to leave in a month or so (before the allowed time has expired) and then come back a week later, would I still only be allowed to stay until Dec 12th, or would I be given 90 days again from when I re-enter?

Thanks.

[immihelp]

90 days again.