Stimulus Breakdown

Hi LSAT Max, I was having a difficult time understanding one of the sentences from the stimulus. Can someone break down: "...since 357 affected live otters and 900 that had died were counted, but only 222 affected otters, or 18 percent of those counted, were successfully rehabilitated and survived" ? I wasn't sure about the information being presented here. Is it trying to say that 900 otters that were saved from the ocean already dead, and 357 that were saved were still alive? Thank you in advance for the help!