Why the double perentesis around to variables?

Working with pyGame and came across this code:

5. DISPLAYSURF = pygame.display.set_mode((400, 300))
Line 5 is a call to the pygame.display.set_mode() function, which returns the 

The ((400, 300)) is what the question is about. Why double perentesis when pygame.display.set_mode() shows only one?
Just something I didn’t understand, I like understanding what and why something is done. Thanks again.

When you invoke a function, the syntax for that uses parentheses
following the function name to enclose its list of variables. In the
example you’ve cited, the first (and only) parameter passed to your
function is a “tuple” (an immutable object sequence). The inner pair
of parentheses around that tuple makes it clear the tuple is the one
parameter to the function, rather than the contents of the tuple
being individual parameters. You can experiment with this yourself
in the REPL:

>>> def foo(bar, baz):
...     print(bar)
...     print(baz)
>>> def xyzzy(plugh):
...     print(plugh)                                                            ...
>>> foo(1,2)
>>> foo((1,2))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: foo() missing 1 required positional argument: 'baz'
>>> xyzzy(1,2)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: xyzzy() takes 1 positional argument but 2 were given
>>> xyzzy((1,2))
(1, 2)