If no credible vote tallies from the conclave leak by the end of June, this resolves to 0% (NO).

If an extremely credible list of every vote and its tallies leaks (say, a Cardinal explicitly and publicly breaks Vatican rules and releases the vote tallies from a journal to a journalist), this resolves to 100% (YES).

If any scenario happens in between, I will resolve to a PROB based on my own subjective reasoning! This might take into account what fraction of the votes were leaked, whether it came from a credible source, whether it aligns with subjective impressions of faithful reporting and accuracy, etc.

For example, what happened after the 2005 conclave would probably resolve to 85-90%:
https://www.foxnews.com/story/cardinal-spills-secrets-from-conclave

I will not vote in this market. If you think that betting on a subjective market will make you annoyed and unhappy, please avoid betting.