That will create textbox which will occupy four rows of text at whatever size the font is set to.
TRUNCATE_TEXT Normally, at textbox will use as many rows it needs to write the text given to it. (It will always respect its width requirement, even to the point of splitting words, though it tries hard to preserve words.) However, sometimes this behavior is undesirable.
Set this to a true value and the height value will be a requirement, not an option.
<textbox w="40%" text="Some text here"/>
<textbox w="60%"><var name="Param1"/> and stuff</textbox>
This will put two textboxes on the page at the current Y-position. The first will occupy 40% of the write-able space and contain the text "Some text here". The second will occupy the rest and contain the text from Param1, then the text " and stuff". (This is the only way to mix parameters and static text in the same textbox.)