noob q about 2257 in video clips
 

I havnt seen any requirement under content guidelines in any of these clips stores like clips.com that say you must add text to yr video clip with a 2257 compliance statement on it. They require the information for their records but I wonder if it also has to be at the beginning or end of a video, is this not the case?
I don't want to make any assumptions when it comes to 2257