The first number is the weapons' normal range
I think you've misunderstood slightly how ranged weapons work.
Quoting from the Basic Rules (freely available online; the above table extract is on p. 48):
Range. A weapon that can be used to make a ranged attack has a range shown in parentheses after the ammunition or thrown property. The range lists two numbers. The first is the weapon's normal range in feet, and the second indicates the weapon's long range. When attacking a target beyond normal range, you have disadvantage on the attack roll. You can't attack a target beyond the weapon's long range.
There are two key things to draw out here:
- Firstly, what those two numbers mean: "The first [number] is the weapon's normal range in feet, and the second [number] indicates the weapon's long range."
- Secondly, what the consequence is of attacking at long range: "When attacking a target beyond normal range, you have disadvantage on the attack roll."
Therefore, you are not at a disadvantage when you use the light crossbow to attack a target up to and including 80 feet away; you are at disadvantage if you make an attack with it at a range farther than 80 feet. You also cannot attack a target beyond 320 feet at all.
You may also have misunderstood ranged attacks in close combat
When you make a ranged attack while in close combat, "you have disadvantage on the attack roll if you are within 5 feet of a hostile creature who can see you and who isn't incapacitated."
In other words, you have disadvantage when you make a ranged attack if there are any hostile creatures within 5 feet of you. That hostile creature might be the creature you're aiming your ranged attack at, but it might not be.
If you're aiming at a creature that's 60 feet away, but you're standing within 5 feet of another hostile creature ("who can see you and who isn't incapacitated"), you'll still have disadvantage on your attack because "[a]iming a ranged attack is more difficult when a foe is next to you."