Yeah, I would say 27 days.

In IVF Land ("The Unhappiest Place on Earth") you count cycle day one only if you bleed before lunchtime. So it makes sense at the other end of the cycle iykwim.

Eta: BG and I obviously don't go to the same clinic
Yep, midday cut off here too.

So if you started a bleed at 8pm on CD27, the next day is CD1.