Well, it’s not that one is right and the other is wrong, but they give slightly different information, according to Oracle docs -
DBA_TAB_PARTITIONS.Blocks: Number of used data blocks in the partition (So…used <= total)
DBA_SEGMENTS.Blocks: Size, in Oracle blocks, of the segment
Docs also mention that the info in dba_tab_partitions comes from collected statistics.
I could join these two views to populate that grid, and have both a “used blocks” and “total blocks” column, but dba_segments is awfully slow in some databases and the extra bit of info may not be worth the added delay of loading that tab. Might be a good thing to put up for a vote in the idea pond.