General question about Browning Sweet Sixteen

[brandbll]

Ok, so i just got a Belgian made Browning Sweet Sixteen from my Grandpa and i'm trying to figure out what the heck this lever on the left hand part of the receiver is.  From what i could gather through google, it's to turn the shotgun from semi-auto to single shot(something about loading heavier shot for geese and what not), but is this correct?

[The General]

My Browning Gold has this exact lever.  I never use it but here is what it's for.  Say you are out shooting ducks and some geese are coming in.  You can pull the lever back, then eject the shell out of the chamber.  The lever doesn't allow the next shell in the magazine to eject so then you can grab a big shell, stick it into the chamber and push the button and be ready in a matter of seconds. 

[brandbll]

Ok, that makes sense, thanks for the help.