If you send a command to this channel, the Level of this channel is set immediately to its target value. When sending a stop command, this level value does not change in Homematic. Your CCU reports the new level (the current level of your blinds/roller shutter) to another channel. In your case, that’d be channel 13.
So OH can never show the “real” level as it just does not know it from this channel the item is linked to.
To send commands to channel 14 and reflect the real level from channel 13, you could use a Proxy item.