Calculate temperature and humidity for 15 minutes

I'm using this code

// Import required libraries
#include "WiFi.h"
#include <Adafruit_Sensor.h>
#include <DHT.h>

#define DHTPIN 27 // Digital pin connected to the DHT sensor

// Uncomment the type of sensor in use:
#define DHTTYPE DHT11 // DHT 11

DHT dht(DHTPIN, DHTTYPE);

String readDHTTemperature() {
// Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
// Read temperature as Celsius (the default)
float t = dht.readTemperature();
// Read temperature as Fahrenheit (isFahrenheit = true)
//float t = dht.readTemperature(true);
// Check if any reads failed and exit early (to try again).
if (isnan(t)) {
Serial.println("Failed to read from DHT sensor!");
return "--";
}
else {
Serial.println(t);
return String(t);
}
}

String readDHTHumidity() {
// Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
float h = dht.readHumidity();
if (isnan(h)) {
Serial.println("Failed to read from DHT sensor!");
return "--";
}
else {
Serial.println(h);
return String(h);
}
}

void setup(){
// Serial port for debugging purposes
Serial.begin(115200);

dht.begin();

readDHTHumidity();
readDHTTemperature();

}

void loop(){

}

to compute the humidity and temperature, now I'm asking how can calculate temperature and humidity for 15 minutes ?

Use millis() for the timing so as not to block the operation of the sketch

See Using millis() for timing. A beginners guide, Several things at the same time and the BlinkWithoutDelay example in the IDE

Probably better to post your code here, not on a site asking for cookie permissions which many people will not do.

Meantime, what does this actually mean?-

updated!

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