question

It's a bit mask, you can find the (complete? @phil.bobo) list of flags by searching for DRAW_FLAG under the main tree, the first result should lead you to MAIN:/project/exec/globals/fsmacros.

Here's the list in 16.2:

#define DRAW_FLAG_BILLBOARD_MASK 0x3
#define DRAW_FLAG_ONE_SIDED 0x4
#define DRAW_FLAG_TWO_SIDED 0x8
#define DRAW_FLAG_NO_DEPTH_TEST 0x10
#define DRAW_FLAG_REFLECTIVE 0x20
#define DRAW_FLAG_LUMINOUS 0x40
#define DRAW_FLAG_SCALE_CHILDREN 0x80
#define DRAW_FLAG_IGNORE_PICKING 0x100
#define DRAW_FLAG_NO_ON_DRAW 0x200
#define DRAW_FLAG_NO_ON_PRE_DRAW 0x400
#define DRAW_FLAG_SKIP_ALL_DRAW 0x800
#define DRAW_FLAG_CENTER_PORT_NAMES 0x1000
#define DRAW_FLAG_INOUT_PORT_NAMES 0x2000

So if you were to set the drawflags attribute to, for example:

DRAW_FLAG_LUMINOUS | DRAW_FLAG_SCALE_CHILDREN

You'd get the equivalent of checking the corresponding boxes in the object's properties.