servo start angle control

In the code I am using two buttons and a servomotor, the buttons are to increase and decrease, the sg90 servo moves from 0 to 180, with the two buttons I want to control the initial angle that is 0, that is, when increasing or decreasing the starting angle, this moves automatically according to that starting angle, for example, if I change it with the buttons to 30, the servomotor moves from 30 to 180 and returns from 180 to 10.

Only the starting angle is modified, and then I want to read it in the serial terminal where it shows me the starting angle that moves and the ending angle that is 180.

#include <Servo.h>
Servo myservo;
int sum=8;
int subtraction=4;
int pos = 0;
int initial = 0;

void setup(){  
  Serial.begin(9600);
  pinMode(sum,INPUT);
  pinMode(subtraction,INPUT);
  myservo.attach(9); 
  myservo.write(pos);
  
}
void loop(){
  myservo.write(pos);
  for(int pos=initial; pos<=180; pos++){
   myservo.write(pos);
   
        Serial.println(pos);

    if(digitalRead(8) == HIGH && initial < 180){
    
    initial = initial + 1;
    
  }
  if(digitalRead(4) == HIGH && initial > 0){
    initial = initial -1 ;
  
  }
   }
      
}

The problem of the code, use a for loop and it does not read well with serial terminal and the movement is not from 0 to 180 and 180 to 0, obviously changing the initial angle according to the buttons, someone can help me.
Thank you

for(int pos=initial; pos<=180; pos++)

The pos variable is already declared above the setup(), I guess there's no reason to it again in the for loop. What exactly is the problem. Describe it better please.

The pos variable declared in the for statement is a different variable from the one declared globally at the top of the program. The compiler knows the difference but this is likely to completely CONFUSE the programmer! It is likely that the programmer intended these to be the same but it is likely that the program will not behave as intended.

The for statement should probably look like this:

for(pos=initial; pos<=180; pos++)

Note that the int declarator has been removed.