Adding to the counter only ONCE while R2 =<200
You can set a flag to indicate that R2 is or has been above 200 since it last was low, much as follows.

// before loop() ...
byte Rhi = true;  // at outset, say that R2 has been high
...

// in loop() ...
  if (R2 &gt; 200)          // Has R2 gone high?
    Rhi = true;
  if (Rhi &amp;&amp; R2 &lt;= 200){ // Has R2 gone low from high?
    Rhi = false;
    ++counter;
    Serial.print("counter: ");
    Serial.println(counter);
  }
  ...