show me how to find the initial value(l_0) using least square method with manual calculation

\begin{tabular}{|c|c|c|c|c|c|c|} \hline n & alpha & Gamma & delta & SSE & & ssquare \\ \hline 16 & 0.2 & 0.1000 & 0.1000 & 25.2171 & & 1.939 \\ \hline & & & & & & \\ \hline time T & & level & growth rate & seasonal factor & last forecast & forecast erro \\ \hline-3 & & & & -14.2162 & & \\ \hline-2 & & & & 6.5529 & & \\ \hline-1 & & & & 18.5721 & & \\ \hline 0 & & 20.8500 & 0.9809 & -10.9088 & & \\ \hline 1 & 10 & 22.3080 & 1.0286 & -14.0254 & 7.6147 & 2.385 \\ \hline 2 & 31 & 23.5587 & 1.0508 & 6.6417 & 29.8895 & 1.110 \\ \hline 3 & 43 & 24.5732 & 1.0472 & 18.5576 & 43.1816 & -0.181 \\ \hline 4 & 16 & 25.8780 & 1.0730 & -10.8057 & 14.7116 & 1.288 \\ \hline 5 & 11 & 26.5659 & 1.0344 & -14.1794 & 12.9256 & -1.925 \\ \hline 6 & 33 & 27.3519 & 1.0096 & 6.5424 & 34.2421 & -1.242 \\ \hline 7 & 45 & 27.9777 & 0.9712 & 18.4040 & 46.9191 & -1.9191 \\ \hline 8 & 17 & 28.7203 & 0.9484 & -10.8972 & 18.1432 & -1.1432 \\ \hline 9 & 14 & 29.3708 & 0.9186 & -14.2986 & 15.4892 & -1.489 \\ \hline 10 & 36 & 30.1230 & 0.9019 & 6.4758 & 36.8317 & -0.831 \\ \hline 11 & 50 & 31.1391 & 0.9134 & 18.4497 & 49.4290 & 0.571 \\ \hline 12 & 21 & 32.0214 & 0.9102 & -10.9096 & 21.1553 & -0.155 \\ \hline 13 & 19 & 33.0051 & 0.9176 & -14.2692 & 18.6331 & 0.3665 \\ \hline 14 & 41 & 34.0430 & 0.9296 & 6.5240 & 40.3985 & 0.6015 \\ \hline 15 & 55 & 35.2881 & 0.9612 & 18.5759 & 53.4223 & 1.577 \\ \hline 16 & 25 & 36.1813 & 0.9544 & -10.9368 & 25.3397 & -0.339 \\ \hline \end{tabular}