Finding out depth on a Survival mode game

I am doing survival mode single player. I am trying to figure out how deep I am. I look at F3 but it does not say current depth. The last group of has something about depth...The lowest I hit is -0.11, when I hit the surface then it reads 0.0, no matter how high I go it stays at 0.0. I am in premade tunnels, game generation. I found 1 large gold vein, like over 100 ore when mined. Nothing since and started a new deep tunnel down. I had to make a way station for food and water. Once I start mining food/water is around 50%. Water was 100% at the entrance. My way station has crops and a chest with block bench so I can follow the red brick marks to the surface. I made small switch backs so when I go down, I do not die jumping down. I also kill spiders, only 2 going to my way station now. Also trying to figure depth for deep underground garden. Has 2 apple trees, 3 plants of corn, tomato, and strawberry. Also looks like a chair but for 1 bucket of water on it for drinking, save using my canteen.

Thank you.

Finally hit the depth I was asking about. From F3....-851 depth, 1 block on top the lava. Pretty cool to see the lava have small waves. Have to see if the garden grows in that area. 100 C temp is insane.