I'd guess it's a 27.2 carbon post epoxied into a 31.8 or 31.6.
The epoxy is not an issue -- it's stronger than the binding force you'd get from tightening a seatpost collar.
The problems may be the length of the carbon post. And whether it was sanded down to fit.
If you can measure the inserted post and it's still 27.2 and it goes a long way -- like 5 or 6 cm -- into the alloy sleeve, the only issues will be aesthetic.
You should just be able to feel how deep it goes by running a spoke or something similar up the bottom.