the amount up or down is literally showing the difference between your balance and what you’ve put in.
If you are down it must mean the share price has dropped more that the amount received in dividends. Check the share price when you first bought and what it is now.
My account is up, but if I subtract the “amount up” from my balance that equals what I have put in. I’ve had a few grands worth of dividends over the past three years and that’s a large part of why I’m up.