This isn't exactly the same as the fins radical, but it's close. Sometimes this will happen (where we have to use a slightly "modified radical" version of the original), so it's good to understand that now, early on. In this case, we have fins. How many fins? Eight fins. How do you know that? Because you caught four fish with two fins each.
After you count and smell all eight of your fins, it's time to put them away. You open a large hatch (はち) and put them in. This is where you keep your fins, always putting in eight at a time because that's what the boss wants.