diff --git a/message_definitions/v1.0/common.xml b/message_definitions/v1.0/common.xml
index 9d7f273ccf..a887a49671 100644
--- a/message_definitions/v1.0/common.xml
+++ b/message_definitions/v1.0/common.xml
@@ -6051,7 +6051,7 @@
       <field type="uint8_t" name="image_status">Current status of image capturing (0: idle, 1: capture in progress, 2: interval set but idle, 3: interval set and capture in progress)</field>
       <field type="uint8_t" name="video_status">Current status of video capturing (0: idle, 1: capture in progress)</field>
       <field type="float" name="image_interval" units="s">Image capture interval</field>
-      <field type="uint32_t" name="recording_time_ms" units="ms">Time since recording started</field>
+      <field type="uint32_t" name="recording_time_ms" units="ms">Elapsed time since recording started (0: Not supported/available). A GCS should compute recording time and use non-zero values of this field to correct any discrepancy.</field>
       <field type="float" name="available_capacity" units="MiB">Available storage capacity.</field>
       <extensions/>
       <field type="int32_t" name="image_count">Total number of images captured ('forever', or until reset using MAV_CMD_STORAGE_FORMAT).</field>