Tool parameters have a multiValue property that can be either true or false.
In the current version, the parameter supports multiple values; however, at the target version, the parameter only supports a single value.
The analyzer applied the following fix to the compatibility issue: a single value was detected in the original model, and that value was saved to the output toolbox.
Use the target version of the software to review the processes in model and script tools that were identified with compatibility issues. Review the version-appropriate tool documentation, run the model or script tool, and review the output to confirm it is acceptable.