When folded back against the wall, the arms of the wall mount have been designed to be leveled when they are correctly folded in.
But, for example, when the TV is back against the wall and the arms are turned completely extended to one side, this can result in the TV being not level exactly. Please make sure you always fold the arms when positioning the TV close to the wall.
The following picture shows the TV against the wall, but the arms extended to one side:
The following picture shows the TV against the wall with arms folded in:
Related article:Wall mounts: When I extend the arms of the wall mount it is drooping a bit; what can I do?