When the screen fonts do not accurately represent the printer fonts (that is, the height-to-width ratio of the printer font is different from that of the screen font), an application can request a smaller font to get the correct width. The application can display the line more quickly and prevent the characters from overlapping using this method.
This behavior can most often be observed when the font vendor does not supply matching screen fonts, or the screen fonts do not contain the same height-to-width ratio as their corresponding printer fonts.