Question for coding Mid-square method in Mathlab

Can somebody please help me to understand this following code?

I don't understand the line 9&10,

s=size(temp); 
st=(s(1,2)/2);.

Also, what I am trying to do is to take 4-digits in the middle of 8-digits squared Seed number (i.e.

seed=7182^2 = 51587124 -> 5811 -> 5811^2 = 33767721)

I don't know why my code is missing 1-digit. I appreciate it if someone helps me with this coding.

Thank you.

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n= input('Enter the length random number : ');
lmt= input('How many number you want to generate: ');
seed=5673;
disp('SN Random Numbers ')
disp('--- -------------- ')
for i=1:lmt
  temp=num2str(seed^2);
  s=size(temp);
  st=(s(1,2)/2);
  x=str2num(temp(st:(st+n-1)));
  fprintf('%d %d\n',i,x);
  seed=x;
end
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[dpb]

size(temp) returns the size of the character string representation of the squared seed value. In MATLAB, even a char string is an array and size() returns the row, column sizes in that order. So, then s(1,2) is the second entry in the s array or the number of columns (characters) in the char() string vector, temp.

This could be written more simply for a single character string as either

st=length(s)/2;     % length returns max(size(s))

or as

st=numel(s)/2;

eliminating the explicit call to size() entirely and the need to subscript it to pull the second value from the s array.

NB: that the division will return a fraction if the character string is ever an odd length.