Google is merely protecting itself from false claims. If you followed the next DMCA step to preserving your rights to the alleged infringing content (and the money you made with your own content) - that would be to counterclaim that the content is it fact yours and the claim sent to you (by Google through the other party) was false... Google is asking you where you wish to go to court if the claimant decided to take the next step (after this one). If this is regards to an Adsense account... the claimant has proof you have been profiteering off their rights (obviously not though since you previously claimed to Google otherwise)... and they wish that back. The problem here lies in your false claim to Google (Adsense) when you sign up for a AdSense account - claimed you would only place adsense on your own content... So Google (on the good faith belief) is acting on your behalf and counterclaiming but need detailed information about where court action will take place. (I'm assuming facts here since you took the content down) You should seek legal advice immediately... BECAUSE if the claimant has pre-registered their copyright the court can award statutory damages up to $150,000 without them ever proving any damage occurred... but the fact that you made money off it with Google Adsense is "actual damages" anyway.
Digging up old threads isn't appropriate... obviously you got yourself in the same jam so hire an attorney!