Thanks for the explanations.
I still don't understand the numbers I'm getting, though.
I did as you suggested and used the "clean" table for my queries.
Now, if I take the modified monthly queries, put them into a spreadsheet, and add them all up, they add up to less than the totals the plugin shows on the dashboard. In fact, the overall total from the beginning of time as calculated by my spreadsheet is less than what the dashboard shows for last month alone.
What am I overlooking?
Oh, wait a minute. Does request_id represent the user, regardless of how many sessions the user has and regardless of how many recordings he/she listens to, and not the session? That might explain it.
If that's the case, then SELECT COUNT(DISTINCT request_id) FROM wp_podlove_downloadintentclean tells me how many total users have attempted to download podcasts on the site since the beginning of time, correct?