When you look at the CSS templates you will see code like this:
.postbit, .postbitlegacy, .eventbit { margin-bottom: {vb:stylevar padding}; display:block; width: 100%; clear:both; position: relative; float: {vb:stylevar left}; color: {vb:stylevar body_color}; border: {vb:stylevar postbit_border}; }
CSS Math
Primarily used within CSS, this is used to evaluate the result of the mathematical expression specified.
{vb:math expression}
An example of this might look like:
height:{vb:math 8px + {vb:math {vb:stylevar font.fontSize}-1}};
This determines the height of an element based on the font size specified in the font style variable and an extra value of 8 pixels.