Round About... what??

I drive through a new round about that has been installed near our home on a fairly frequent basis. You all know the concept: traffic flows in a circle; if there's someone coming from your left, you wait until the traffic is clear before entering the round about. After you're in, you travel in a counter clockwise direction as long as you want to stay in the round about.  You have the right of way (except for changing lanes within a multiple land round about) until you exit. The ONLY way in is to turn right. The ONLY way out is to turn right. If there are two lanes that enter a two lane round about, the ONLY way in is to still turn right: right turn from the right lane entering into the outer lane of the round about, right turn from the left lane entering into the inner lane of the round about.

So you ask, why am I stating the obvious?? It doesn't take a civil engineering degree to figure this out.  So here's the punch line:
Explain to me what the three headed arrow means at the entry way to this round about:

However,  I'm pretty sure that turning LEFT into a round about is a bad idea, even if the traffic is light.  Going straight doesn't seem like an especially bright idea either, as there's no road in front of me... just the center of the round about.

Please explain what I'm missing....