A: Depending on the model you use and the feature you use, different kind of credits are deduced.

here is the model wise credit standards:
https://www.getmerlin.in/query-standards

(We can't say the exact credit usage for feature use. Though for large input features like chat with docs, pdfs and websites. Credits used will be higher. For small input features like a 5 minute youtube video, it will be lower.)