multiplication table cleaned up and commented

maxNum = int(input("What number do you want to go up to? ")) + 1

firstColumnJustifyWidth = len(str(maxNum))
justifyWidth = firstColumnJustifyWidth**2 # Rough guess at how much we'll need to space things out
if justifyWidth == 1: # For 0 < x < 9
    justifyWidth += 1

headerNumbers = ['X'.rjust(firstColumnJustifyWidth)] # Start off with just the 'X'
for columnNumber in range(1, maxNum): # For each column
    headerNumbers.append(str(columnNumber).rjust(justifyWidth)) # Add all the header numbers into the list...
print(' '.join(headerNumbers)) # Join the list together with at least one space

for rowNumber in range(1, maxNum): # For each row...
    formattedRowNumber = str(rowNumber).rjust(firstColumnJustifyWidth) # Format the row number for printing
    rowData = []
    for columnNumber in range(1, maxNum):
        rowData.append(str(rowNumber * columnNumber).rjust(justifyWidth)) # For each column: Do the multiplication and format the result for printing
    formattedRowData = ' '.join(rowData) # Join the list together with at least one space
    print(formattedRowNumber + ' ' + formattedRowData)