about XPM problem?

[=?big5?b?tsC8eSBLYXNvbiBIdWFuZw==?= <kasonhuang kinposh com cn>]

hello:
how are you?
anyone know  in the  line "13  13  5  2  7  7" ,"2" "7" and "7"  what meaning?

/* XPM */
static char * roundb_xpm[] = {
/* width height ncolors cpp [x_hot y_hot] */
"13 13 5 2 7 7",
/* colors */
"  s none	m none	c none",
". s topShadowColor m white c lightblue",
"X s iconColor1 m black c black",
"o s bottomShadowColor m black c #646464646464",
"O s selectColor m white c red",
/* pixels */
"                          ",
"          . . .           ",
"      . . X X X o o       ",
"    . X X X X X X X o     ",
"    . X X X X X X X o     ",
"  . X X X X O X X X X o   ",
"  . X X X O O O X X X o   ",
"  . X X X X O X X X X o   ",
"    . X X X X X X X o     ",
"    . X X X X X X X o     ",
"      o o X X X o o       ",
"          o o o           ",
"                          "
}; 


ps: could someone tell me where could I find a detail story about XPM.

Thanks in advance.
kason