That would depend on on the origin and or manufacture. Some would measure bb center to top seattube, others measure bb center to toptube center. Toptubes are always measured center to center(ctc). English bikes are in inches center to top, most French are metric center to top, a lot of Italian are measured metric center to center, but I see many Roma ctt. Also there is the standover height. On to of that there is the sellers measuring, that can be all over the board on how they record.