Have a look at the garment measurements to work out your size… the XS is very small (young teen size) and the size you choose will depend of the kind of fit you’d like. See photos for the same size (S) jumper on 3 different sized people.

Finished Garment Measurements: Note: The length of the garment and sleeves are easily adjusted at points marked in the pattern. You may require extra yarn.
Back of neck to hem: 40 (44, 44, 51, 56, 56)cm 15.5 (17, 17, 20, 22, 22”) can be adjusted as desired
Sleeve underarm: 31cm (31, 31, 35, 35, 35) 12 ¼ (12 ¼, 12 ¼, 13 ½, 13 ½, 13 ½)” approx
Chest circumference: 80 (94, 106, 115, 124 131)cm 31.5 (37, 42, 45, 49, 51.5)”
Arm circumference at underarm: 27 (33, 35.5, 38, 40, 44.5)cm 10 ¾ (13, 14, 15, 16, 17 ¾ )”

You will need: 4 (5, 5, 6, 6, 7) skeins of Plump Superchunky in main colour A (shown in Pavlova), 1 skein of Plump Superchunky in contrast colour B (shown in Damson Jam), 1 skein of Plump Superchunky in contrast colour C (shown in Raspberry Ripple)
12mm circular needles (at least 80cm)
12mm dpns or 40cm circular needles for sleeves and start of jumper
10mm circulars or dpns for neck and ribs
Stitch markers
Stitch holders