It may be useful to clear up a couple of technical points about Peirce’s terminology before getting to the main business.
Here I’m using extension and intension in the conventional sense that concerns the extension and intension of a concept or term. We define a concept or term in extension by giving all the things falling under it. We define a concept or term in intension by giving all the properties it implies or falls under. The parallel morphology of the words “extension” and “intension” is pleasing enough to ear and eye that we usually just let it go at that, but punctilious pedants long ago noticed the fly in the ointment that an extension is a many, a set of things, while an intension is a one, a single property or quality, and so they insist on the technical term comprehension to signify a collection of intensions. In practice, of course, context of application will determine how picky we need to be.