You should not have to use credits to make minor revisions to an AI video if it didn't come out right the first time.

Hi Tila-az1!

Thanks for writing in. Please note that each image/ video generation, even when using the same prompt or settings, consumes credits as the system processes a new render each time. However, we’ll share your feedback with the team for consideration. 

Let us know if you have any questions.

Kartika