Not only are the 706 planets only potential candidates, but I believe they include all possible planets, not just the "earthlike" planets. The article is poorly written in that manner, and the headline here is magnifying the error.
That said, 306 of the 706 have already been confirm. No stats on the number or percentage of false positives in that first batch.
The article is quite clear - "NASA's Kepler spacecraft hunting for Earth-like planets around other stars has found 706 candidates for potential alien worlds while gazing at more than 156,000 stars packed into a single patch of the sky."
Potential. No claim that any of them are 'earth-like'. The person who wrote the title either doesn't know how to read or is being deliberately sensationalist.
That said, 306 of the 706 have already been confirm. No stats on the number or percentage of false positives in that first batch.