How to change fontsize with pygame_gui?

Question

New to this package, unsure how to change a labe like this:

Want to make the font size larger...

problem_label = pygame_gui.elements.UILabel(
    relative_rect=pygame.Rect((300, 100), (200, 80)),
    text= generate_problem(),
    manager=manager,
)

Tried some online stuff, documentation wasn't helpful.