brushless motor speed

hi ,
this is my first question here so please help me :wink:
i’m trying to make a quadcopter based on arduino , so i’m using brushless motor with and esc controller
my question is what is the speed of motors correspondent to the value that i write in this function " ServoWriteMicroseconds() "
for example : if i enter 1000 in wich speed of motos correspondent
if i put 1300 → …

That depends on many factors. Particular firmwares may give you more control over this,
this isn't a quadcopter forum though, there are better places to ask about this.

One question for you: Before driving a car do you ask what the mapping between gas pedal
angle and engine rpm is?