update creating_an_annotation_task.md (#4231)

site/content/en/docs/manual/basics/creating_an_annotation_task.md

@@ -82,45 +82,48 @@ For more information on how to attach cloud storage, see [attach cloud storage](
 
 ### Data formats for a 3D task
 
-To create a 3D task, you need to use the following directory structures:
+To create a 3D task, you must prepare an archive with one of the following directory structures:
 {{< tabpane >}}
   {{< tab header="Velodyne" >}}
     VELODYNE FORMAT
     Structure:
-    velodyne_points/
-    data/
-    image_01.bin
-    IMAGE_00 # unknown dirname, Generally image_01.png can be under IMAGE_00, IMAGE_01, IMAGE_02, IMAGE_03, etc
-    data/
-    image_01.png
+      velodyne_points/
+        data/
+          image_01.bin
+          IMAGE_00 # unknown dirname,
+                   # generally image_01.png can be under IMAGE_00, IMAGE_01, IMAGE_02, IMAGE_03, etc
+      data/
+        image_01.png
   {{< /tab >}}
   {{< tab header="3D pointcloud" >}}
     3D POINTCLOUD DATA FORMAT
     Structure:
-    pointcloud/
-    00001.pcd
-    related_images/
-    00001_pcd/
-    image_01.png # or any other image
+      pointcloud/
+        00001.pcd
+      related_images/
+        00001_pcd/
+          image_01.png # or any other image
   {{< /tab >}}
   {{< tab header="3D Option 1" >}}
     3D, DEFAULT DATAFORMAT Option 1
     Structure:
-    data/
-    image.pcd
-    image.png
+      data/
+        image.pcd
+        image.png
   {{< /tab >}}
   {{< tab header="3D Option 2" >}}
     3D, DEFAULT DATAFORMAT Option 2
     Structure:
-    data/
-    image_1/
-    image_1.pcd
-    context_1.png # or any other name
-    context_2.jpg
+      data/
+        image_1/
+            image_1.pcd
+            context_1.png # or any other name
+            context_2.jpg
   {{< /tab >}}
 {{< /tabpane >}}
 
+> You can't mix 2D and 3D data in the same task.
+
 ## Advanced configuration
 
 ![](/images/image128.jpg)