The Per-Tree Summaries report involves the concepts of in-bag and out-of-bag observations. For an individual tree, the bootstrap sample of observations used in fitting the tree is drawn with replacement. Even if you specify that 100% of the observations are to be sampled, because they are drawn with replacement, the expected proportion of unused observations is 1/e. For each individual tree, the unused observations are called the out-of-bag observations. The observations used in fitting the tree are called in-bag observations.