HUD question

[smanj440]

The indicator for my health says 1000/1000 on the left side when I open my cuff links, and there is like an extension to the right of it sort of connected to it that says like 293 or some other number. What does that mean? It seems to be a part of the health indicator. Thanks

[Phoenix]

It's how much blood left in current bloodbag that Sam uses.

[Kittenpox]

Your 1000/1000 is the available blood in your own body - your health bar, essentially. The 293 (presumably out of 500) is the amount of blood remaining in the current blood bag, as Phoenix said.

If you take damage, whether by taking a bad fall, being shot, etc. then after a little bit there will be a transfusion and the bag will be automatically used to refill your body.
You can also eat Cryptobiotes if you need health in a hurry, but if you're carrying blood bags that rarely becomes an issue.

During the course of the game you can acquire Hematic grenades / weapons that fire Hematic rounds - and those will drain from any equipped blood bag first, then switch to using your body's blood supply if no available bags remain.

With the Utility Pouch*, you can store four blood bags without them contributing to the cargo on your back. If those get used up you can open your inventory, discard the empty bags, and auto-arrange your inventory to move ones from your back to the pouch.
* I think that's an unlock you get along the way, though, so it might not be immediately available.