When you click collection, you can see your collection, but not the entire collection because each member likes to view their collection in different ways. Some like to see it by sport, some by set, some by team, some by player. Plus, you can create different collections within your collection. For instance, I have a separated collection for my team sets because I collection a Topps set of Detroit Tigers each year and put them in a separate binder. I also collect the entire flagship and update sets and those are in my standard collection. If they were combined, it would say I have two 2022 Topps Miguel Cabrera, card #194. I do indeed own two, but I collect one for the team set and one for the complete set for the year. I also have a separate collection of cards that I have listed on ebay so that when they sell, I can remove them from here and vice versa. It allows a lot of flexibility for each individual user.
The trick to remember is if you get into trading, selling or buying using the transaction feature here, any cards you receive will automatically go into your standard collection. You will need to manually move them to any other collections later if you do make more than one collection.
Again, welcome and good luck!