Come on, Giz...you know someone always leaves a backdoor open....at the very least for administration purposes.
The great eye that sees all suggests nothing so nefarious as hackers, so let's go with administrative activity. There were some post registration event cancellations that made the available seats appear to go up since those events now show available in the data. Then some of the Gygax family and friends were added to open events which made the available seat count go down.
As of 2018-02-23_08-57-14 number of events: 1,502 featured events: 202 events with 467 of 1,657 seats available total_seats: 11,251, available_seats: 4,016
As of 2018-02-26_10-50-42 number of events: 1,502 featured events: 202 events with 430 of 1,658 seats available total_seats: 11,244, available_seats: 3,736
As of 2018-02-27_08-15-22 number of events: 1,502 featured events: 202 events with 424 of 1,658 seats available total_seats: 11,244, available_seats: 3,704
As of 2018-03-01_10-22-55 number of events: 1,502 featured events: 202 events with 423 of 1,657 seats available total_seats: 11,243, available_seats: 3,714
Penultimate day of data collection As of 2018-03-05_10-55-24 number of events: 1,502 featured events: 202 events with 430 of 1,657 seats available total_seats: 11,243, available_seats: 3,775
probably last day of data collection As of 2018-03-06_09-37-36 number of events: 1,502 featured events: 202 events with 441 of 1,657 seats available total_seats: 11,243, available_seats: 3,816