There are apparently two lines for every channel. There are two options:
The first is to simply plot the first row rather than both rows:
plot(Ch1(1,4:end), 'g', 'DisplayName','Channel 1')
the second is to return a handle from each plot call:
C1h = plot(Ch1(1,4:end), 'g', 'DisplayName','Channel 1');
and then in the legend call, provide only one element for each plot:
figure
Ch1h = plot(rand(10,2),'g','DisplayName','First Line');
hold on
Ch2h = plot(rand(10,2),'m','DisplayName','Second Line');
hold off
legend([Ch1h(1),Ch2h(1)], 'Location','best')
I cannot write exact cold without your data, however one of these approaches should work.
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