message: Explain origin of magic number
diff: @@ -116,7 +116,7 @@ limitations under the License.
  position: absolute;
  left: -15px;
  border-radius: 0 3px 3px 0;
  - top: -8px; // (16px / 2)
  + top: -8px; // (16px from height / 2)
  }
  .mx_TagPanel .mx_TagTile.mx_AccessibleButton:focus {
  