But you plotted against ordinal number of observation...
plot((SMed_eq),'-r','Marker','*','LineWidth',1.3);
hold on
plot((SMed_eq_ne),'-g','Marker','*','LineWidth',1.3);
Use
x=0:length(SMed_g)-1;
plot(x,SMed_eq,'-r','Marker','*','LineWidth',1.3);
etc., instead and you can then just set xlim limits to
xlim([0 UP])
where UP is whatever you want for visual effect as the upper x-axis limit. tick labels will match ticks and start at 0 for both with no machinations needed.
As is, you'd need to do something like
hAx=gca;
xtk=hAx.XTick;
hAx.XTickLabel=xtk-1;
but it's simpler to just use the desired x coordinates against which to plot().