Thaweddb is not included in the calculation of the total index size when measuring maxTotalDataSizeMB.
Keep in mind that Splunk will stop indexing when there are only 2 Gig of diskspace available. If you have limited diskspace (default maxTotalDataSizeMB per index is 500Gig) and you wish to search on some old buckets in thaweddb, be mindful of how much diskspace you have available so indexing is not interrupted.