22st to 28r on 4mm needles = 4 inches/10cm

From the SIRDAR website:
Hayfield Baby Double Knitting is a great value, great quality Hayfield yarn. It has a fantastic 70% acrylic, 30% nylon blend in a 100g format. Baby DK is enjoyable to knit with and comes with a wide range of designs and colours, including pretty pastels and fun brights. Hayfield Baby Double Knitting is easy to knit and easy care, making it the perfect all round baby yarn.

Blend: 70% Acrylic, 30% Nylon
Ball weight: 100g
Yardage: 350m approx / 383y approx
Needle size: 4mm
Tension: 22 stitches, 28 rows to 4 inches / 10cm on 4mm needles