Excerpt uploaded extra text I did not wanted.

Hello everyone, may be you can give me a little of your expertise.

I uploaded a bunch of videos from youtube, and the except came in, but it uploaded a bunch of more text I wanted. How do I go around erasing the part I do not want.

Thankfully, all the extra text is the same. Is there a way to erase it without opening every post (about 400 of them). Thank you