The agglomeration schedule is a numerical summary of the cluster solution. At the first stage, cases 8 and 11 are combined because they have the smallest distance. The cluster created by their joining next appears in stage 7. In stage 7, the clusters created in stages 1 and 3 are joined. The resulting cluster next appears in stage 8. When there are many cases, this table becomes rather long, but it may be easier to scan the coefficients column for large gaps rather than scan the dendrogram. A good cluster solution sees a sudden jump (gap) in the distance coefficient. The solution before the gap indicates the good solution. The largest gaps in the coefficients column occur between stages 5 and 6, indicating a 6-cluster solution, and stages 9 and 10, indicating a 2-cluster solution. These are the same as your findings from the dendrogram. This is somewhat unsatisfactory as a solution, because there isn't a strong classification. Try a solution using complete linkage (Furthest neighbor) as the cluster method.