You can try this I kinda half-arsed it though. I personally could not see the issue in your code other than the fact that you are writing bad/ugly code. I don’t mean it in a rude way, you should read other people’s code and understand the conventions. Besides that, I think the issue is with the delays.

// This is a lot more understandable now
#define ENTRY_FINISH_PIN 8
#define ENTRY_NUMBER_PIN 9
#define ENTRY_REPORT_PIN 13

#define ENTRY_DELAY_MS 500
#define ENTRY_REPORT_SHOW_MS 500
#define ENTRY_REPORT_WAIT_MS 100

int GetNumber()
{
    // loop until ENTRY_FINISH_PIN is HIGH
    // if ENTRY_NUMBER_PIN is HIGH, add to the iterant and turn on the LED
    // after that wait a bit and turn off LED
    
    int iterant = 0;
    while (digitalRead(ENTRY_FINISH_PIN) != HIGH) {
        if (digitalRead(ENTRY_NUMBER_PIN == HIGH)) {
            iterant++;

            digitalWrite(ENTRY_REPORT_PIN, HIGH);
        }

        delay(ENTRY_DELAY_MS);
        digitalWrite(ENTRY_REPORT_PIN, LOW);
    }
    
    return iterant;
}

void setup()
{
    pinMode(ENTRY_FINISH_PIN, INPUT);
    pinMode(ENTRY_NUMBER_PIN, INPUT);
    pinMode(ENTRY_REPORT_PIN, OUTPUT);
}

void loop()
{
    int sum = GetNumber() + GetNumber();

    for (int i = 0; i < sum; i++) {
        digitalWrite(ENTRY_REPORT_PIN, HIGH);
        delay(ENTRY_REPORT_SHOW_MS);
        digitalWrite(ENTRY_REPORT_PIN, LOW);
        delay(ENTRY_REPORT_WAIT_MS); // waiting a bit more makes sense imo
    }
}

I wish u luck with your Arduino adventure ^^