Why is there extra space after the last column in a Tkinter application?

I’m trying to build an application in Tkinter. When the user presses a button, I need 3 widgets to appear in certain rows and columns. When the user clicks again, I need 3 more widgets (of the same types) to appear to the right of the first ones. Do this until 5 widgets are on a row, then go to the next row. I managed to determine exactly where I want them to appear, but I can’t explain to myself why there’s some extra space after the last column, but not before the first one.

import tkinter as tk
import customtkinter
from tkinter import messagebox

root = tk.Tk()

root.minsize(1100, 650)
root.iconbitmap('textures/logo.ico')
root.title('Diceware')

global number_of_dicerolls
number_of_dicerolls = 0

# Give a weight to rows 0 to 15
i = 0
while i <= 15:
    root.grid_rowconfigure(i, weight=1, uniform='row')
    i += 1

# Give a weight to columns 0 to 9
i = 0
while i <= 9:
    root.grid_columnconfigure(i, weight=1, uniform='column')
    i += 1


def display_words():
    """
    Called when the user clicks the 'roll dice' button,
    this function displays the pairs of dice rolls and words to the user.
    """
    global number_of_dicerolls
    if number_of_dicerolls < 35:
        column_to_be_placed_in = (number_of_dicerolls % 5) * 2
        number_of_dicerolls += 1

        diceroll_widget = customtkinter.CTkTextbox(root, height=1)
        diceroll_widget.insert('1.0', 'Hello, world!')
        diceroll_widget.grid(row=2 + 2 * ((number_of_dicerolls - 1) // 5),
                             column=column_to_be_placed_in,
                             pady=(5, 0), padx=10)

        word_widget = customtkinter.CTkTextbox(root, height=1)
        word_widget.insert('1.0', 'Goodbye, world!')
        word_widget.grid(row=3 + 2 * ((number_of_dicerolls - 1) // 5),
                         column=column_to_be_placed_in,
                         sticky='n', pady=(0, 5), padx=10)

        test_var = tk.IntVar()
        checkbox = customtkinter.CTkCheckBox(master=root,
                                             variable=test_var, text='',
                                             checkbox_width=20,
                                             checkbox_height=20, fg_color='gray',
                                             hover_color='white')
        checkbox.grid(row=3 + 2 * ((number_of_dicerolls - 1) // 5),  column=column_to_be_placed_in + 1,
                      sticky='w')
    else:
        answer = tk.messagebox.askquestion('Dice roll limit reached',
                                           'You have reached the maximum limit of 35 dice rolls. Do you want '
                                           'to clear the screen?', parent=root)
        if answer == 'yes':
            clear_window()


roll_dice_button = customtkinter.CTkButton(root, border_width=2, border_color='black', text='ROLL DICE',
                                           fg_color='blue', hover_color='gray',
                                           command=display_words)
roll_dice_button.grid(row=0, column=0, columnspan=10, pady=0, sticky='n')

root.mainloop()

I tried adding some sticky attributes to the widgets, I tried messing around with the weight of the columns and rows, I tried removing the uniform attriburtes of the rows and columns in an attempt to solve this issue, I tried specifically setting padx, pady, ipadx and ipady to 0, but to no avail. The widgets moved around as expected (the checkboxes weren’t sticked to the west when I removed the ‘sticky’ attribute, for example), but that space after the last column, but not before the first one, remained.