What components are on your Bike? STI is a trade name shimano invented

Shimano Front shifter goes ka thunk A B or C .. Double- A/B no adjustment other than the cage shape

thats why it looks so Funny

Old bikes and ones with bar end shifters the pull on the cable is the lever
its just friction vs the return spring on the orther end pulling back

Maybe a trip back to the shop where you bought the Bike* is in order so someone in the room can show you
what you ask about, here where no one can do hands on Demos.

or most others too .. if it's actually out of whack the cost to straighten it out wont be much.