tarmac Sl6 says min 75mm of seat post insertion (which this frame looks based on). I'm 185cm and 817mm saddle height (top of saddle to center of BB) and on a 58cm this works out to 817-40(seat to rail)-522(C-T)=255 exposed seat tube. On a 350mm seat post, that's 95mm insertion depth.
*edit
I missed your column showing 240mm, so that works out to 110mm min insertion assuming we trust the painted scale on the back. @lachlan383 you broke the frame at 20mm under min insertion or 90mm total insertion?
