need help for commands used in coding

 [A,B]=xlsread('ground','Sheet1');

Ip=A(:,3);
Vp=A(:,6);
Vs=A(:,9);
dV=(Vp-Vs);
plot(Ip,dV)
%axis([-50 50 -300 300])
axis off
saveas(gcf,'A1.jpg')
a=imread('A1.jpg');
imshow(a)
c=rgb2gray(a);
imshow(c)
count=0;
for i= 1:900
    for j= 1:1200
        if c(i,j)>1
            if c(i,j)<220         
                count=count+1;
            end;
        end;
    end;
end;
display(count)

this is the code for which I need help ,I am not able to understand how the coding is done ,please help me to understand the coding...

[Walter Roberson]

Could you be more specific about which parts you do not understand?

[Manali Kulkarni]

Sir, I just want to understand the command %axis([-50 50 -300 300]),what happened is when I am taking different values instead of above mentioned the program produces error and the thing is that this program was given as an assignment to me and I have to explain the working of this one but I am not getting it ,the thing I have understood is that using some values stored in excel sheet an image is obtained and that image is converted from rgb to grey ,then the count is determined by using the loop but I am not clear about the values chosen ,on what basis these values have been decided....please help...