Why can't the barber understand me when I say I want my hair trimed?

I wanted to get my semi-long wavy hair trimed, you know have them only take a little bit off the sides to make it look nicer. I have asked multiple barbers to do this and then they all my cut hair really short. Why? How can I get them to only take a little off?Why can't the barber understand me when I say I want my hair trimed?
You need to be really specific with how you want it cutWhy can't the barber understand me when I say I want my hair trimed?
they do what they want i always go and get my sides trimmed and the back trimmed to and then i say take off like a centimeter off my eye and they take off a inch so it doesnt even cover my eye anymore.
Haha, say you wont tip them if they cut too much off. That will probably get them to listen to you.