I poked around the internet to try to learn about the net-meter meter (ours is made by General Electric). It appears that it flashes through a few different displays. If I read correctly, the number shown when code=100 indicates the amount of power that's been imported. the number shown when code=101 indicates the amount of power that's been exported.
According to what I read, the blocky arrow thingy indicates whether power is being imported or exported at any given moment (equivalent to looking at the spin direction on the antique one).