My I suggest that you buy a copy of John Adams book "reading fish finders" I think that is the title It is without a doubt the best publication you will ever get your hands on about fish finders
If you want to know what your sounder is telling you his book will tell and more importantly show you exactly whats what.

I've put a post called Furuno 620 and have 3 screen shots.  Hope they help. 

 thanks ctan they look awesome I have read that book just good too see live shots as some ground around were I fish is really hard to understand as there is not many lump just rumble and little ledgers 

try putting your range on 10m and program your function key so its the shift button then you can keep following the bottom up or down. having your gain on auto in <40m is your best bet aswell. because the screen is so small run you pic advance at 1/1.

the ground in the bay is pretty small but holds a few fish through the cooler months now till the ban is probably the best time to fish it. look between 24 and 28

heres a couple from the bay..

an edge with little pinks on

a nugget with a few bigger ones

coral with a couple of bigger fish

 thanks heaps man they look wicked it's always good to see what peoples setting are for the area we fish thanks heaps that really put in my mind there are fish in bunbury I just have to find them cheers