Eruvin 83: Up the Down Staircase

Standardized measurements are not yet in place in the time of the Talmud. So what size is a se'ah? There's a range presented on the daf, in a bit of a whirlwind. Also - Residents of two-story homes that open to the courtyard who forgot to make an eruv - and what it means to be upstairs when it comes to exiting to the courtyard, or downstairs and sharing space with the upstairs people.