that line is correct coz that production is not added in that state
@Mk Utkarsh
yes, because it shouldnot
add that state
Check the rule
lookahead1 is lookahead to that $A$ in red color ${\color{Red} A}\rightarrow a.A,a|b$
And that $A$ comes from prev. state
And in prev state
we got $A\rightarrow .aA$ which again has no follow set
So, go to prev production again, i.e. $S\rightarrow .AA$
And from here we got value of $Follow\left ( A \right )=\left \{ a,b \right \}$
Ok??