To get rid of the extra space inside the listbox, you can specify its size (in pixels):
list = {'1','2','3'};
[indx]=listdlg( ...
'PromptString',{'Select Number.',''},...
'SelectionMode','single', ...
'ListString',list, ...
'ListSize',[100 120]); % 100 pixels wide, 120 pixels high
To get rid of the extra space above the listbox, you can avoid sending it empty lines in the PromptString:
list = {'1','2','3'};
[indx]=listdlg( ...
'PromptString','Select Number.',...
'SelectionMode','single', ...
'ListString',list, ...
'ListSize',[100 120]);
Unfortunately, increasing the font size is not as easy as specifying an additional pair of input arguments.
