So basically, this area is known as the depolarization period. And what that means is, because of the rapid opening of many of these voltage gated sodium ion channels, we have a rapid influx of these sodium ions into the cell. And so many of these positively charged sodium ions move into the cell. And that makes the inside of the cell positive with respect to the outside. And that's exactly why we increase the value to about positive 30 millivolts. Now, notice it increases, but we don't actually get to the positive 60 millivolt value, which is what the sodium voltage is at equilibrium.