Equation Coding in GAMS environment

Question

everybody, there is a constraint called k4 I want to code but I don't know how to achieve it. How I can write this equation in the GAMS environment? The k4 constraint I want to encode is as in the picture:

I think, I coded all constraints (k1, k2, k3, k5, k6, k7 k8, and k9) except k4. Unfortunately, I don't know how I code constraint k4 that is seen in the picture.

constraint k4

My code is as follows:

Sets
t      /0*15/
i      /1*6/
m      /1*4/
k      /1*3/;

Alias(i,j);

Parameter

p(i)
/1  0  
 2  2
 3  5
 4  3
 5  3
 6  0/;

Parameter

Prec(i,j);

Prec("1","2") = 1;
Prec("1","3") = 1;
Prec("2","4") = 1;
Prec("3","5") = 1;
Prec("4","6") = 1;
Prec("5","6") = 1;

Table S(m,k)
    1   2   3
1   0   1   1
2   1   0   1
3   1   0   0   
4   1   0   1;

Table b(i,k)
    1   2   3
1   0   0   0
2   0   1   1
3   1   0   1   
4   2   1   0
5   0   1   0
6   0   0   0;

Variables

st(i)
obj;

Binary Variables

x(i,m,t)
y(i,m,k)
z(i,t);

Equations

amac, k1, k2, k3, k4, k5, k6, k7, k8, k9;

amac(i).. obj =e= sum(t, z(i,t)*ord(t));
k1(i).. st(i) =e= sum(t, z(i,t)*ord(t));
k2(i,j)$(Prec(i,j)).. st(i)+p(i) =l= st(j);
k3(i,m,t).. x(i,m,t) =l= 1;
k4(t).. sum((i,d), x(i,m,d)) =l= 1;
k5(i,m,t).. x(i,m,t) =l= z(i,t);
k6(i,m,t).. x(i,m,t)+1 =l= z(i,t)+sum(k, y(i,m,k));
k7(i,m,k).. y(i,m,k) =l= S(m,k);
k8(i,k).. sum(m, y(i,m,k)) =e= b(i,k);
k9(i,m).. sum(t, x(i,m,t)) =e= sum(k, y(i,m,k));

Model MSRCPSP /all/;

Solve MSRCPSP using MIP minimizing obj;

Display x.l, y.l, z.l;