Nothing important I've been told. My dealer said it was just a reminder that at that point you have a full (1) battery. My suspicion is that if your 12v battery starts playing up that might turn a different colour.
I've read it in one of the manuals somewhere but I can't find it for the life of me at the moment. Certain what's circled though is essentially indicating the "Primary (1) fuel source" gauge (if it's a hybrid it'd have the 2) - bit like the little petrol pump icon you get on an ICE.
12v battery warning light is slightly different:
HV warning light is also separate (missing the one and in a different place and, I think, orange)
Now that I've stared at it a bit, its what Billy The Kid said, but its a bit confusing. Here:
The picture of the battery with the 1 next to it is just part of the label for the whole 'chargemeter' on the left. So you wont ever see that little battery picture change or do anything, its just part of the label. In the same way, the words 'power' and 'charge' are the labels for the power-output/regen meter on the right. Its just a label.
Hope my red line and green arrows make it a bit more obvious.