Always Read the Manual

I've finally figured out why my baking always gets burnt on top before it's completely cooked through.
Duh... wrong oven setting. =.= I guess I always knew this at the back of my head but can't figure out why it's wrong. I mean, I only have 3 settings on my oven. The first one is without fan, the other one is with fan, and the third one... I don't know what it is so I never used it. So i've always used the second setting.

Today I decided to try the third one...
OMG I almost set off the smoke detector alarm again! My unit went all smokey... :S

So I immediately turned off my oven, opened my door and window and started fanning like a stupid idiot (I'm SO glad there's nobody out on the corridor at that time) Then dashed off to look for a manual. Couldn't find one. Luckily for technology nowadays, everything is online. So I found the manual online.

Guess what?

The third setting was the correct setting (yea, you probably thought otherwise :P). The second one I've been using all this while is like.. super double heat grill whatever thing which makes the top a lot hotter. =.=
so WHY did the oven go all smokey!??

I think it's just because I've never used the third setting before which is something like 'circular heating' which i believe means heat all round?
And the smokey smell today wasn't a burnt food smell.. it was worse :S
The manual asks to "Operate the oven for about 30 minutes at maximum temperature to burn off all traces of grease which might otherwise create unpleasant smells when cooking."
Maybe the circular heating thing heats up places in the oven I've never tried before....
That could explain the nasty smells and smokiness... right????

So the question now is....
How do I make sure this setting is usable next time without setting off the alarm??