I could work this out for you... if I had all the unknowns... which h there are many.
An easy model would be to assume that the gas in the mason jar is 100% saturated steam at 212 degrees F. After capping the jar, the steam cools and condenses to a liquid.
I the thing to consider is the unknowns... like... what is the actual mix of air and steam... what is the actual temperature of the gas... the liquid... what gas volume is lost when the lid deform inward... how does the volume of the jar change when cooled?
How about we just accept that it works and have a beer instead?
If you knew me better you'd understand--such a perfectly sensible, obvious thing would never occur.
Just a note of thanks here, as usual a little overdue: I've gotten side-tracked at the moment but plan to do some more scratching later.
Again, Thanks.