"rising" interrupts behaves as "chance" on mega2560

Other Hardware Sensors
13

im already used 5v by 10k pot as voltage divider.
i tried again
and plotted interrupt function change according to the pin2 voltage
two test made

blue: interrupt function
red : pin2 voltage
on arduino nano

if voltage goes up the interrupt called only one times(when voltage level reached 2,5v)

blue: interrupt function
red : pin2 voltage
on arduino mega

if voltage between 2,3v to 2,5v interrupt goes looping and blue line high

codes

unsigned long delays=0;
int sayi=0, voltage=0,durum2=0;
bool durum=false;
void setup() {
 // pinMode(2 ,INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(2), say, RISING);

  Serial.begin(9600);
}
void say() {  sayi++; durum=true;}

void loop() {

if ((millis()-delays)>=50)
{    
delays=millis();

  // Serial.print("durum=");


 if (durum)
 { 
  durum=false; 
  durum2=5000;
    Serial.print(durum2);
  Serial.print(" ");
  }
  else{
    durum2=1000;
      Serial.print(durum2);
  Serial.print(" ");}
  voltage=analogRead(A0);
  voltage=map(voltage,0,1023,0,5000);
  Serial.println(voltage);
}
}
Interrupt maximum timing and HI/LOW specs