Question about custom login background

[Stein 0]

I am creating a custom login background with the help of the wiki: http://herc.ws/wiki/Login_Background

 

So far everything works fine. I'm just wondering why there is a 4th row of textures for the Background since you just need 12 splits (3 rows) and not 16. Also: why is there .bmp and .tga format? It works well with .bmp only.

 

 

"t_¹è°æ1-1.bmp", "t_¹è°æ1-2.bmp", "t_¹è°æ1-3.bmp", "t_¹è°æ1-4.bmp"

"t_¹è°æ2-1.bmp", "t_¹è°æ2-2.bmp", "t_¹è°æ2-3.bmp", "t_¹è°æ2-4.bmp"
"t_¹è°æ3-1.bmp", "t_¹è°æ3-2.bmp", "t_¹è°æ3-3.bmp", "t_¹è°æ3-4.bmp"
"t_¹è°æ4-1.bmp", "t_¹è°æ4-2.bmp", "t_¹è°æ4-3.bmp", "t_¹è°æ4-4.bmp"

 

"t_¹è°æ1-1.tga", "t_¹è°æ1-2.tga", "t_¹è°æ1-3.tga", "t_¹è°æ1-4.tga"
"t_¹è°æ2-1.tga", "t_¹è°æ2-2.tga", "t_¹è°æ2-3.tga", "t_¹è°æ2-4.tga"
"t_¹è°æ3-1.tga", "t_¹è°æ3-2.tga", "t_¹è°æ3-3.tga", "t_¹è°æ3-4.tga"
"t_¹è°æ4-1.tga", "t_¹è°æ4-2.tga", "t_¹è°æ4-3.tga", "t_¹è°æ4-4.tga"