Size labels too small in products page

Hi,

I am building a website using the Phlox theme and I am having issues with how sizes are displaying for clothes in Woocommerce.

Please have a look here https://dsntrendz.com/product/two-piece-tracksuit-2/ to see what I mean.

Can anyone advise me where I can alter these settings so that the sizes display correctly?

Regards
Dave

The page I need help with: [log in to see the link]