When you read about a medical study, you're seeing a snapshot of research at one point in time. Sometimes, after that snapshot is published, the researchers need to issue a correction, called an erratum. This is a normal, if not glamorous, part of science—it means the authors are clarifying something in their original work.
The details of this particular correction aren't provided. We don't know what condition was studied, what treatment was tested, or what the original results were. We also don't know what specifically needed to be corrected—it could be a minor typo in a chart, a clarification about how the analysis was done, or something more significant.
What this means for you is simple: it's a reminder that science is a process of building knowledge, and that process includes checking work and making updates. When you see that a study has been corrected, it's a sign of that process at work. It doesn't automatically mean the original study was wrong, but it does mean the most accurate version of the record now includes this update. Always look for the most current version of any research you're reading about.