Hi,
If you are drawing the content in the 2D symbol and there is nothing in the 2D script then:
it will scale to the A and B values.(Width and Length, Dimension 1 and Dimension 2 Values)
If you add FRAGMENT2 ALL,0 to the empty 2d script, then it will be just the size of your original drawing (it will ignore the bounding box and place your object at its original size.
if you only want specific layers shown(out of the 16 layers available in the 2D symbol) have a FRAGMENT2 command for each layer rather than all,
i.e.
FRAGMENT2 1,0 to show layer 1
FRAGMENT2 4,0 to show layer 4
FRAGMENT2 5,0 to show layer 5
the internal layers of the 2D symbol is just a way to store 16 different drawings in the same object, Archicad does not use them in the project.
if you want something scale sensitive then...
different drawing shown for different scales:
if GLOB_SCALE >= 100 then FRAGMENT2 1,0
if GLOB_SCALE >= 50 and GLOB_SCALE < 100 then FRAGMENT2 2,0
if GLOB_SCALE < 50 then FRAGMENT2 3,0
or more information shown when the scale increases
FRAGMENT2 1,0
if GLOB_SCALE < 100 then FRAGMENT2 2,0
if GLOB_SCALE < 50 then FRAGMENT2 3,0
you can move the 2d elements in the 2d symbol to the different layers the same way you normally do in archicad, using the the layer drop down in the info box.(the default layer you draw on is layer 1) the above example uses layer 1 for drawings 1:100 or higher, layer 2 for 1:50 and layer 3 for 1:20 scale drawings. GLOB_SCALE is the built in variable that tells GDL the scale of the current view, as an integer i.e. at 1:100 GLOB_SCALE is 100.
If there is script in the 2D Script area then:
if there is a Mul2 A/1.50000, B/2.500000 in the 2D script, then this will also re-scale your object to the bounding box.(the numbers dividing the A and B will be the original size of the object) delete the Mul2 line from the code to fix this.
There are many other things that might affect the scaling of the library part as listed by Lasz and Barry.