How to add up values with loop

Hello,

I have a problem with replication of my calculations in Excel to script.

I have data set like on the picture belowe.

I created matrix 15x6 with values from yellow columns and I want to calculate values in blue and orange ones.

For aclculating blue ones I used code:

d=15;
ss=[2,2,1,3,1,4,1,1,3,2,2,3,4,1,1]

Tp = readtable("SA_sekw/data_in.xlsx",'Sheet', "Sheet2",'Range', "C2:F8", "ReadVariableNames",true);
Tp = Tp{:,:};
m = length(Tp(:,1));
fp=zeros(d,m+1);
fm=zeros(d,m+1);
Tps=zeros(d,m+1); 
    for k=1:m;    %loop for calculating from input data 15x6 "yelow" matrix
        for i=2:d;
           Tps(i,k)=Tp(k,ss(1,i));
        end;
    end;

for dd=1:3    % recalcuating if some value was "0" in previous iteration.
   for i=2:d; %loop for calculating "blue" PW value for each row and column
       for k=1:m;
            val_fp=(Tps(i-1,k+1)+fp(i-1,k+1)-Tps(i,k)); % replicated excel formula
            if val_fp <0;
               fp(i,k)=0;
             else
               fp(i,k)=val_fp;
            end;
        end;
    end;
end;
disp(fp)

And I menaged to calulate output like below:

disp(fp)
     0     0     0     0     0     0     0
     0     0     0     0     0     0     0
     0     7   411   451     4     0     0
     0   122    55     0     0     0     0
   298    24    73   529   517     0     0
   346     0   451   485     0     0     0
     0   102   561   240     0     0     0
   405   145   229    55    79     0     0
    76     0     0    50     0     0     0
   302   437     0   107   121     0     0
   398   475    95   150     0     0     0
     0   229   176   367     0     0     0
   424   479   373   442   332     0     0
   448    24   518   572     0     0     0
   327   102   561    55    79     0     0

Question is:

WHY values for fp(1:4,1) , fp(1:2,2), fp(1:3,3), fp(1:2,4) are incorrect ?

If i start from i=1:d then script is looking for row number 0 in first iteration.

Any tip will be helpfull.