This modification of the system only pertains to the Download solution since all the files are located on your server and can be modified. Always be sure you have downloaded the latest build of PHP Live! from the client area and upgraded your system so that the file and line information is accurate.
There are few variables that sets the embed chat window width and height and also the popup chat window width and height. The following are the default values:
$VARS_CHAT_WIDTH = 600 ;
The $VARS_CHAT_WIDTH and $VARS_CHAT_HEIGHT sets the popup chat widow dimensions.
The $VARS_CHAT_WIDTH_WIDGET and $VARS_CHAT_HEIGHT_WIDGET sets the embed chat window dimensions.
For procedures to update the default values, please refer to the Improve server performance by adjusting some PHP Live! variables documentation.