diff --git a/data-organization/Annotation-JSON-format/04_Supervisely_Format_objects.md b/data-organization/Annotation-JSON-format/04_Supervisely_Format_objects.md
index 0eaa0354..d79dea43 100644
--- a/data-organization/Annotation-JSON-format/04_Supervisely_Format_objects.md
+++ b/data-organization/Annotation-JSON-format/04_Supervisely_Format_objects.md
@@ -326,7 +326,7 @@ Fields description:
 - `classTitle` - string - the title of the current class. It's used to identify the corresponding class shape from the `meta.json` file 
 - `bitmap` - object with two fields:
   - `origin`  - points (`x` and `y` coordinates) of the top left corner of the bitmap, i.e. the position of the bitmap within the image
-  - `data`  - string - encoded representation of a string
+  - `data`  - string - encoded representation of a boolean matrix