fix: clarify RTC channel subscription requirements in create.mdx (#1614)

Author: saudsami

cloud-transcoding/rest-api/create.mdx

@@ -97,7 +97,7 @@ The `tokenName` you obtained in the response body of the `Acquire` method. See [
               When the audio input source is RTC, this object is required.
 
               <Parameter name="rtcChannel" type="string" required={true}>
-              The RTC channel name for the audio input source. Currently, only audio and video sources that subscribe to a single channel are supported. The audio source and video source must belong to the same channel.
+              The RTC channel name for the audio input source. Currently, you can only subscribe to audio and video sources from a single channel; the audio and video sources must belong to the same channel.
               </Parameter>
 
               <Parameter name="rtcUid" type="number" required={true}>
@@ -125,13 +125,13 @@ The `tokenName` you obtained in the response body of the `Acquire` method. See [
             - `1`: Play the media stream once.
             - `-1`: Play the media stream in a loop.
             - `n`: Specify the number of times to play the media stream. Cannot be set to 0.
-            </Parameter>            
+            </Parameter>
 
             <Parameter name="rtc" type="object" required={false}>
               This object is required when the video input source is RTC.
 
               <Parameter name="rtcChannel" type="string" required={true}>
-              The RTC channel name for the video input source. Currently, only audio and video sources that subscribe to a single channel are supported. The audio source and video source must belong to the same channel.
+              The RTC channel name for the video input source. Currently, you can only subscribe to audio and video sources from a single channel; the audio and video sources must belong to the same channel.
               </Parameter>
 
               <Parameter name="rtcUid" type="number" required={true}>
@@ -234,7 +234,7 @@ The `tokenName` you obtained in the response body of the `Acquire` method. See [
           </Parameter>
 
           <Parameter name="outputs" type="array" required={true}>
-            Configure output settings to publish to an RTC channel or CDN address.
+            Configure output settings to publish to a single RTC channel or CDN address.
 
             You must specify either `streamUrl` or `rtc`.
 
@@ -243,7 +243,7 @@ The `tokenName` you obtained in the response body of the `Acquire` method. See [
             </Parameter>
 
             <Parameter name="rtc" type="object" required={true}>
-              Required for publishing to an RTC channel.
+              Required for publishing to an RTC channel. Currently, you can publish to only one RTC channel.
 
               <Parameter name="rtcChannel" type="string" required={true}>
               The RTC channel name for the transcoded audio and video.