The raw index of a sample, i.e. the index as if would be used with RawFrameDataView and NOT an Item ID as it would be used with HierarchyFrameDataView.
Note: When HierarchyFrameDataView uses HierarchyFrameDataView.ViewMode.MergeSamplesWithTheSameName mode, Unity merges multiple samples with the same name at the same hierarchy level together in a single item.
As a result of this behavior, and the hierarchical structure of the samples in HierarchyFrameDataView, the Hierarchy item identifiers that HierarchyFrameDataView uses, do not correspond to the sample indices that RawFrameDataView uses.
When working with HierarchyFrameDataView, use HierarchyFrameDataView.GetItemRawFrameDataViewIndices to get the sample indices in a format that works with ProfilerTimeSampleSelection and use HierarchyFrameDataView.ItemContainsRawFrameDataViewIndex to check if a selected sample index corresponds to a HierarchyFrameDataView item..
Additional resources: rawSampleIndices, RawFrameDataView, HierarchyFrameDataView.GetItemRawFrameDataViewIndices and HierarchyFrameDataView.ItemContainsRawFrameDataViewIndex.