About Pole locations are more than 10% in error

I want to make a Luenberger observer , and this is my code :

G = c2d(G2,0.004);

tf = G;

I = eye(11);

pi = 100000;

U = 1;

x0=[0;0;0;0;0;0;0;0;0;0;0];

x=zeros(11,1250);

x(:,1)=x0;

A = [0.1321 -1.287 -0.03492 -0.5931 0.02748 -0.183 0.1432 -0.07204 0.02407 -0.002951 0.0007733;

1 0 0 0 0 0 0 0 0 0 0;

0 1 0 0 0 0 0 0 0 0 0;

0 0 1 0 0 0 0 0 0 0 0;

0 0 0 1 0 0 0 0 0 0 0;

0 0 0 0 0.5 0 0 0 0 0 0;

0 0 0 0 0 0.125 0 0 0 0 0;

0 0 0 0 0 0 0.0625 0 0 0 0;

0 0 0 0 0 0 0 0.03125 0 0 0;

0 0 0 0 0 0 0 0 0.003906 0 0;

0 0 0 0 0 0 0 0 0 0.0004883 0];

B = [2;

0;

0;

0;

0;

0;

0;

0;

0;

0;

0];

C = [0.3156 -0.04226 0.4169 0.009387 0.197 -0.008443 0.4791 -0.3495 0.1721 -0.3119 0.1723];

p = [1.01 0.95 0.94 1.02 0.8 0.8 0.97 0.7 0.99 0.9 1.003 ];

L = acker(A',C',p);

data = textread('Data 0.003-4.3 [y0].txt');

y = data(:, 3);

u = data(:, 4);

k=1:1:1250;

for i=1:1250

x(:,i+1) = A*x(:,i)+B*u(i)+L'*(y(i)-C*x(:,i));

y1(i) = C*x(:,i);

end

figure(1)

plot(k,y)

figure(2)

plot(k,y1)

but i get this Warning: [Pole locations are more than 10% in error.]

could anybody teach me how to solve this problem. Thanks!