sometimes you can see schools of 'fish' and they won't bite, we've all had that to happen.
also fishfinders will pick up big balls if bait fish the the fish ID will sometimes get confused and ID as larger fish.
Fish ID's are shown when the fishfinder shows what it thinks is a fish,..not everything it ID's is a fish, IE debris,bubbles,etc..
several youtube videos will help you set-up and use your fish finders. There's also a fishfinder section on this forum that people
use to show fishfinder pictures with explanations of what they are seeing. Check you area for local guides, ask them if they will
help you look at your fishfinder,..you may find one that will do just that...