The ironing symbol lets you know that you can iron a garment or fabric. However the dots let you know what temperature you can iron at.

Hot iron to 210o max

Cotton, linen viscose and derivatives of viscose.

Warm iron 150o max

Wool, Polyester mixtures.

Cool iron 110o max

Acrylic, nylon, acetates and polyester.

DO NOT IRON

Plasticised materials & some Acrylics.