There seems to be an issue with the color that gets plotted over the contour. I just plotted the contour afterwards with good results. (Small note: There is an error in your code: "length(us)" has to be "length(s)")
data = readtable('https://mathworks.com/matlabcentral/answers/uploaded_files/1482526/for_testing.txt');
J = 10;
x = data{:,1}; y = data{:, 2}; z = data{:, 3}; c = data{:, J}; % check the number of columns of your input.
a = unique(x); s = unique(y); g = unique(z);
data_sorted = sortrows(data, 1:J);
v = reshape(data_sorted{:,J}, length(s), length(g));
f=figure;
%f.Position = [100 100 1340 940]; % commented for better readability in the browser (can be removed)
ax = axes();
hold(ax);
% removed contour(...) from here
p=pcolor(s,g,v);
p.FaceAlpha = 0.85;
axis([s(1) 70 g(1) g(120)]);
shading interp;
colormap(flipud(jet))
% moved contour(...) here VVVV
l=contour(s,g,v,[0.008 0.02 0.05 0.1 0.3],'k','LineWidth',1.8,'ShowText','on','LabelSpacing',300);
c=colorbar();
caxis([0.0 0.5]);
