Why doesn't clock.tick() measure time accurately in Pygame?

Question

I've created a simple game in Pygame that displays an image of a certain emotion for x amount of time, before giving participants the opportunity to select which emotion was displayed by pressing a button. However, I'm having trouble maintaining the display time for images. I use clock.tick() to get a value for delta time, but it seems that it's 3x slower than it should be. If I set the timer to 1000ms, for example, the image is displayed for ~3 seconds, whereas I only want it to display for 1 second. I can always divide the display time by 3 to get it roughly correct, but I want to understand what's causing this. Here's the main game loop:

def mainGame(images):
dt = 0    #delta time is set to 0 to begin
timer = displayTime #displayTime by default is 1000ms
imageNumber = 0
gameState = States.VIEWING    #this is the game state where a participant views a question
running = True
while running:
    mouse = pygame.mouse.get_pos()
    screen.fill((255, 255, 255))
    mainDisplay()             #this displays the answer buttons
    clock = pygame.time.Clock()
    
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            running = False
        elif event.type == pygame.KEYDOWN:
            if event.key == pygame.K_ESCAPE:
                running = False


    if ( gameState == States.VIEWING):
        dt = clock.tick_busy_loop(30)   #should increase delta time by however many ms have passed
        timer -= dt                     #minus delta time from the timer
        if timer >= 0:                  #if the timer remains above 0, continue displaying image
            askQuestion(images, imageNumber)
        else:                           #when timer reaches 0, stop displaying image and move to answering state
            gameState = States.ANSWERING
            

    elif (gameState == States.ANSWERING):     #this is where participants select their answer
        timer = displayTime                   #reset the timer
        screen.fill((255, 255, 255))
        mainDisplay()                         #displays answer buttons
        for emotion, rects in rectDict.items(): #this detects whether a button has been clicked or not
            if event.type == pygame.MOUSEBUTTONDOWN:
                if rects.collidepoint(mouse):            #if a button is clicked
                    gameState = States.VIEWING           #switch back to viewing state
                    answers.append(emotion)                 #add answer to answer list
                    imageNumber += 1                    #move to the next image
                elif not any(rect.collidepoint(mouse) for rect in rectList):   #if a button is not clicked
                    print("You did not select an answer")
                    break

    if practice == True:   #if in practice mood, stop when number of practice questions is reached
        if len(answers) == pnumberofQuestions:
            break
    elif practice == False: #if in main game loop, stop when number of questions is reached
        if len(answers) == numberofQuestions:
            break

    pygame.display.update()

Answer 1

You are creating a new clock each pass through the while loop.

Move

    clock = pygame.time.Clock()

out of your

while running:

and put it somewhere above it.