right lemme see if I can remember what my endo told me baaaaack in the day.
SHBG is sex binding hemoglobin which kinda... chomps T and makes it unavailable to your body. So it basically nullfies it?
having low SHBG means you're likely to have a lot of FREE testosterone in your system, t that isn't bound and is therefore quite free to be used by your cells. (they should have actually tested your t and included a number on "free testosterone" but sometimes they don't do this for some reason.) This often will result in things like excessive body hair, acne, thinning hair etc. You know, general T side effects but to a much lower degree as the amount of free t floating around is still fairly low due to you producing less than a cis man would (though usually more than a cis woman because their T is usually mostly bound by the shbg)
It means that they may want to start you on a lower dose of t and monitor to see what your body does with it.
But free T basically means "biochemically available" and active. Bound T is effectively inert and useless.
Googling "free testosterone" might explain a bit better but that's how I understand it from the lecture my gyno gave me all those years ago lol.