Sets the text size which is the height scale factor of the text boundary (DXF 40). This factor influences on the text width and text height together and is used for proportional scaling of letters, spaces, and the text boundary. A value less than 1.0 decreases the text. A value greater than 1.0 increases the text. The initial value is 0.0 by default. 

Example of Working with the Text Style Record Object 

Specific Properties of Text Styles 

OdDbTextStyleTableRecord::textSize() method