Hi there! Thanks for reaching out to TRIANGL Support. For bottoms, the difference is:
XXS: waist 59 to 62 cm, hips 85 to 89 cm
XS: waist 63 to 66 cm, hips 90 to 94 cm
So XS is the next size up from XXS.
Replies are sent through Open Doors, so they stay on the customer record.