Index exceeds matrix dimensions23

hello, you know how it can?

lgg=2...24
lt=1..5
ltmax=5
thetavSP(1,lt)=(thetaO+deltathetaa1(1,lt));
..
thetavprec(lt)=thetavSP(1,lt);
..
thetavSP(lgg,lt)=thetavSP(lgg-1,ltmax)+deltathetaa1(lgg,lt);

Index exceeds matrix dimensions.

Error in primavera (line 1097)
thetavSP(lgg,lt)=thetavSP(lgg-1,ltmax)+deltathetaa1(lgg,lt);