Click the
Configure Download Metadata button
The first screen (level) applies to All/any sources. Note the ticks to the right.
(I dislike bulk Tags, so I remove the tick, no need to fine tune below)
BUT Kovid allows us to
Cherry Pick and provides us with a button at the bottom that allows us to choose what source provides what part of the data.
I prefer Series from 'A', Comments from 'C', so I select "A" from the list, then click the button,
You also get to change the Cover source Priority
Remove ticks from the list on the left that are not likly to benefit, it speeds up retrieval.