The scale statement for the scale drawing of the chair is "Scale: 1 : 20"

Looking at the scale statement (without looking at the scale drawing) indicates that the actual chair is 20 times the size of of the chair in the scale drawing.

The 40 cm in the scale drawing above indicates that the the actual scale ratio is "Scale: 1 cm : 20 cm". When the units are the same (in this case both units are centimetres) and some indication of length and units are given in the scale drawing, it is possible to leave the units out of the scale statement.

The following could also have been used as scale statements in the scale drawing: