What is the current status of submitted manuscript?
The associate-editor is the person who is handling your manuscript. He is not the person doing the reviews. The associate editor send some e-mails to some researchers to invite people to review your papers. These reviewers will submit their reviews and then the associate editor will make a decision on your manuscript based on these reviews.  The decision could be something like : accept, reject or need to be revised.
So there is no conflicts between these two status. An associate editor was assigned to handle your paper. Then, &quot;under review&quot; means that the associate editor has already invited some persons to review your paper and that at least one of them has already accepted.  Now, it can take some time before all the reviews are submitted... sometimes weeks or months. Then eventually you will get the result.