That's the simple way of saying it.
Really it's eleven episodes, followed by the TV "good end", epiode 12, which just ends the series without following the manga.
Then there are four episodes broadcast online that make the "true end", starting off from the "real" episode 12, up to episode 15. These follow the manga.
All in all, 16 episodes.
1>2>3>4>5>6>7>8>9>10>11>12 ("good end")
1>2>3>4>5>6>7>8>9>10>11|>12>13>14>15 ("true end")