How to interpret Prometheus exporter memory metrics

Versions (relevant - OpenSearch/Dashboard/Server OS/Browser):
Opensearch 2.12.0

Describe the issue:
We’re trying to bring down the memory use on our data nodes and discovered 2 metrics from the Prometheus exporter: opensearch_indices_segments_memory_bytes and opensearch_index_segments_memory_bytes. I would have assumed that the _indices_ metrics would be roughly equal to the sum of all of the _index_ metrics on a particular host, but the total of the _index_ metrics is almost 40x the _indices_ metrics. What do these 2 metrics mean?

We have quite a number of Jaeger indices that have large _index_ values type=bitset. We only see _index_ values from our active Logstash write index.
Are the Jaeger indices being stored in a suboptimal way?