Xrandr Not All Resolutions Seen

So I have two monitors, a laptop monitor and an lcd which I use as a second screen when my laptop is docked, and I'm able to set it up with xrandr to set it up to work fine-ish. The code I use is

Code:

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xrandr --output VGA --right-of LVDS --mode 1024x768

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And it works, and my monitor is now right of the laptop screen. The problem I'm having is when I do xrandr -q to find out what all the resolutions are for the VGA I don't see the highest one of 1280x1024 instead I see:

Code:

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VGA connected 1024x768+1280+0 (normal left inverted right x axis y axis) 338mm x 270mm
  1152x768      54.8 
  1024x768      60.0*
  832x624        74.6 
  800x600        72.2    75.0    60.3    56.2 
  640x480        85.0    72.8    75.0    60.0 
  720x400        85.0 
  640x400        85.1 
  640x350        85.1

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Any ideas how I can get this up to the optimal resolution.?

most of this problems are solved when you edit your xorg.conf file. Or you can try whith a program called X an then write to your xorg.conf file from there.
also visit this place
xorg.conf(5x) manual page

I understand that, but that problem that I'm having is that I don't know what to edit because this isn't my main screen, rather it's a second screen that's only used some of the time.