If that gauge is in it's own window you should be able to...
right-click on it
left-click on "undock window"
grab a corner with your mouse and resize it to what you want
right-click on it
left-click on "undock window"
A more permanent solution would require a panel.cfg edit.
This is from a plane I have with that gauge...
Quote:[Window11]
Background_color=16,16,16
size_mm=239,65
window_size_ratio=1.000
position=0
visible=0
ident=330
window_size= 0.300, 0.110
window_pos= 0.240, 0.790
The highlighted text sets the size of the window as a percentage of the size of the panel.
Changing that line to window_size= 0.150,0.055 //0.300, 0.110
re-sizes that window. Note: FS will ignore everything on that line after "//" so you can retain the original setting for future reference.
If you have further questions or your panel.cfg is set up different than this, post back with what it looks like.
cheers,
Joe